Er4Fe29Si5 crystallizes in the triclinic P-1 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 19-coordinate geometry to one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(14), one Fe(2), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(1), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(7), one Si(1), and one Si(2) atom. In the second Er site, Er(2) is bonded in a 19-coordinate geometry to one Fe(1), one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(15), one Fe(16), one Fe(4), one Fe(6), one Fe(9), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(8), and one Si(3) atom. There are sixteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Er(2), two equivalent Er(1), one Fe(10), one Fe(11), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(7), one Si(1), and one Si(2) atom to form distorted FeEr3Fe7Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra, and faces with three equivalent Fe(11)Er2Fe8Si2 cuboctahedra. In the second Fe site, Fe(2) is bonded to one Er(1), two equivalent Er(2), one Fe(12), one Fe(15), one Fe(16), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(8), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. In the third Fe site, Fe(3) is bonded to one Er(1), two equivalent Er(2), one Fe(10), one Fe(12), one Fe(13), one Fe(16), one Fe(2), one Fe(6), one Fe(8), one Fe(9), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(14)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. In the fourth Fe site, Fe(4) is bonded to one Er(2), two equivalent Er(1), one Fe(1), one Fe(10), one Fe(11), one Fe(13), one Fe(5), one Fe(7), one Fe(9), one Si(1), and one Si(2) atom to form distorted FeEr3Fe7Si2 cuboctahedra that share  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(2)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, and faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra. In the fifth Fe site, Fe(5) is bonded to one Er(1), two equivalent Er(2), one Fe(11), one Fe(12), one Fe(13), one Fe(15), one Fe(2), one Fe(4), one Fe(8), one Fe(9), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra. In the sixth Fe site, Fe(6) is bonded to one Er(2), two equivalent Er(1), one Fe(1), one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(14), one Fe(3), one Fe(7), and one Si(2) atom to form distorted FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(2)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(6)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, and faces with three equivalent Fe(11)Er2Fe8Si2 cuboctahedra. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Er(1), one Fe(10), one Fe(11), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(1), one Si(1), and two equivalent Si(2) atoms. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Er(2), one Fe(12), one Fe(15), one Fe(16), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(2), and two equivalent Si(3) atoms. In the ninth Fe site, Fe(9) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(12), one Fe(13), one Fe(16), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(8), and two equivalent Si(3) atoms. In the tenth Fe site, Fe(10) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(1), one Fe(11), one Fe(13), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Si(1), and two equivalent Si(2) atoms. In the eleventh Fe site, Fe(11) is bonded to one Er(1), one Er(2), one Fe(1), one Fe(10), one Fe(13), one Fe(14), one Fe(4), one Fe(5), one Fe(6), one Fe(7), and two equivalent Si(2) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, faces with three equivalent Fe(1)Er3Fe7Si2 cuboctahedra, and faces with three equivalent Fe(6)Er3Fe8Si cuboctahedra. In the twelfth Fe site, Fe(12) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(13), one Fe(15), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(8), one Fe(9), and two equivalent Si(3) atoms. In the thirteenth Fe site, Fe(13) is bonded to one Er(1), one Er(2), one Fe(10), one Fe(11), one Fe(12), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(9), one Si(2), and one Si(3) atom to form distorted FeEr2Fe8Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with three equivalent Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, and  a faceface with one Fe(6)Er3Fe8Si cuboctahedra. In the fourteenth Fe site, Fe(14) is bonded to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(11), two equivalent Fe(6), two equivalent Fe(7), and two equivalent Si(2) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, and faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra. In the fifteenth Fe site, Fe(15) is bonded to two equivalent Er(2), two equivalent Fe(12), two equivalent Fe(2), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(3) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, edges with two equivalent Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. In the sixteenth Fe site, Fe(16) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(8), two equivalent Fe(9), and two equivalent Si(3) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(6)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(10), two equivalent Fe(4), two equivalent Fe(7), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 14-coordinate geometry to one Er(1), one Fe(1), one Fe(13), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(10), two equivalent Fe(11), two equivalent Fe(7), one Si(1), and one Si(2) atom. In the third Si site, Si(3) is bonded in a 14-coordinate geometry to one Er(2), one Fe(13), one Fe(15), one Fe(16), one Fe(2), one Fe(3), one Fe(5), two equivalent Fe(12), two equivalent Fe(8), two equivalent Fe(9), and one Si(3) atom.
Er4Fe29Si5 crystallizes in the triclinic P-1 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 19-coordinate geometry to one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(14), one Fe(2), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(1), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(7), one Si(1), and one Si(2) atom. The Er(1)-Fe(10) bond length is 2.91 Å. The Er(1)-Fe(11) bond length is 2.92 Å. The Er(1)-Fe(12) bond length is 2.91 Å. The Er(1)-Fe(13) bond length is 3.26 Å. The Er(1)-Fe(14) bond length is 3.24 Å. The Er(1)-Fe(2) bond length is 3.14 Å. The Er(1)-Fe(3) bond length is 3.02 Å. The Er(1)-Fe(5) bond length is 3.01 Å. The Er(1)-Fe(9) bond length is 2.90 Å. There is one shorter (3.05 Å) and one longer (3.15 Å) Er(1)-Fe(1) bond length. There is one shorter (3.16 Å) and one longer (3.17 Å) Er(1)-Fe(4) bond length. There is one shorter (3.14 Å) and one longer (3.20 Å) Er(1)-Fe(6) bond length. There is one shorter (2.87 Å) and one longer (2.90 Å) Er(1)-Fe(7) bond length. The Er(1)-Si(1) bond length is 3.30 Å. The Er(1)-Si(2) bond length is 3.05 Å. In the second Er site, Er(2) is bonded in a 19-coordinate geometry to one Fe(1), one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(15), one Fe(16), one Fe(4), one Fe(6), one Fe(9), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(8), and one Si(3) atom. The Er(2)-Fe(1) bond length is 3.16 Å. The Er(2)-Fe(10) bond length is 2.88 Å. The Er(2)-Fe(11) bond length is 2.94 Å. The Er(2)-Fe(12) bond length is 2.93 Å. The Er(2)-Fe(13) bond length is 3.26 Å. The Er(2)-Fe(15) bond length is 3.27 Å. The Er(2)-Fe(16) bond length is 3.29 Å. The Er(2)-Fe(4) bond length is 3.03 Å. The Er(2)-Fe(6) bond length is 2.99 Å. The Er(2)-Fe(9) bond length is 2.92 Å. There is one shorter (3.02 Å) and one longer (3.20 Å) Er(2)-Fe(2) bond length. There is one shorter (3.15 Å) and one longer (3.17 Å) Er(2)-Fe(3) bond length. There is one shorter (3.15 Å) and one longer (3.19 Å) Er(2)-Fe(5) bond length. There is one shorter (2.91 Å) and one longer (2.92 Å) Er(2)-Fe(8) bond length. The Er(2)-Si(3) bond length is 3.04 Å. There are sixteen inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Er(2), two equivalent Er(1), one Fe(10), one Fe(11), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(7), one Si(1), and one Si(2) atom to form distorted FeEr3Fe7Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra, and faces with three equivalent Fe(11)Er2Fe8Si2 cuboctahedra. The Fe(1)-Fe(10) bond length is 2.52 Å. The Fe(1)-Fe(11) bond length is 2.50 Å. The Fe(1)-Fe(14) bond length is 2.39 Å. The Fe(1)-Fe(4) bond length is 2.47 Å. The Fe(1)-Fe(6) bond length is 2.41 Å. There is one shorter (2.52 Å) and one longer (2.55 Å) Fe(1)-Fe(7) bond length. The Fe(1)-Si(1) bond length is 2.36 Å. The Fe(1)-Si(2) bond length is 2.59 Å. In the second Fe site, Fe(2) is bonded to one Er(1), two equivalent Er(2), one Fe(12), one Fe(15), one Fe(16), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(8), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. The Fe(2)-Fe(12) bond length is 2.51 Å. The Fe(2)-Fe(15) bond length is 2.40 Å. The Fe(2)-Fe(16) bond length is 2.39 Å. The Fe(2)-Fe(3) bond length is 2.43 Å. The Fe(2)-Fe(5) bond length is 2.42 Å. The Fe(2)-Fe(9) bond length is 2.52 Å. Both Fe(2)-Fe(8) bond lengths are 2.56 Å. The Fe(2)-Si(3) bond length is 2.54 Å. In the third Fe site, Fe(3) is bonded to one Er(1), two equivalent Er(2), one Fe(10), one Fe(12), one Fe(13), one Fe(16), one Fe(2), one Fe(6), one Fe(8), one Fe(9), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(14)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. The Fe(3)-Fe(10) bond length is 2.55 Å. The Fe(3)-Fe(12) bond length is 2.51 Å. The Fe(3)-Fe(13) bond length is 2.40 Å. The Fe(3)-Fe(16) bond length is 2.38 Å. The Fe(3)-Fe(6) bond length is 2.41 Å. The Fe(3)-Fe(8) bond length is 2.52 Å. The Fe(3)-Fe(9) bond length is 2.56 Å. The Fe(3)-Si(3) bond length is 2.54 Å. In the fourth Fe site, Fe(4) is bonded to one Er(2), two equivalent Er(1), one Fe(1), one Fe(10), one Fe(11), one Fe(13), one Fe(5), one Fe(7), one Fe(9), one Si(1), and one Si(2) atom to form distorted FeEr3Fe7Si2 cuboctahedra that share  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(2)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, and faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra. The Fe(4)-Fe(10) bond length is 2.53 Å. The Fe(4)-Fe(11) bond length is 2.50 Å. The Fe(4)-Fe(13) bond length is 2.39 Å. The Fe(4)-Fe(5) bond length is 2.43 Å. The Fe(4)-Fe(7) bond length is 2.52 Å. The Fe(4)-Fe(9) bond length is 2.56 Å. The Fe(4)-Si(1) bond length is 2.36 Å. The Fe(4)-Si(2) bond length is 2.58 Å. In the fifth Fe site, Fe(5) is bonded to one Er(1), two equivalent Er(2), one Fe(11), one Fe(12), one Fe(13), one Fe(15), one Fe(2), one Fe(4), one Fe(8), one Fe(9), and one Si(3) atom to form FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(14)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(16)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra. The Fe(5)-Fe(11) bond length is 2.58 Å. The Fe(5)-Fe(12) bond length is 2.57 Å. The Fe(5)-Fe(13) bond length is 2.39 Å. The Fe(5)-Fe(15) bond length is 2.39 Å. The Fe(5)-Fe(8) bond length is 2.52 Å. The Fe(5)-Fe(9) bond length is 2.51 Å. The Fe(5)-Si(3) bond length is 2.56 Å. In the sixth Fe site, Fe(6) is bonded to one Er(2), two equivalent Er(1), one Fe(1), one Fe(10), one Fe(11), one Fe(12), one Fe(13), one Fe(14), one Fe(3), one Fe(7), and one Si(2) atom to form distorted FeEr3Fe8Si cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(2)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(6)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, and faces with three equivalent Fe(11)Er2Fe8Si2 cuboctahedra. The Fe(6)-Fe(10) bond length is 2.53 Å. The Fe(6)-Fe(11) bond length is 2.58 Å. The Fe(6)-Fe(12) bond length is 2.56 Å. The Fe(6)-Fe(13) bond length is 2.40 Å. The Fe(6)-Fe(14) bond length is 2.40 Å. The Fe(6)-Fe(7) bond length is 2.52 Å. The Fe(6)-Si(2) bond length is 2.48 Å. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Er(1), one Fe(10), one Fe(11), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(1), one Si(1), and two equivalent Si(2) atoms. The Fe(7)-Fe(10) bond length is 2.51 Å. The Fe(7)-Fe(11) bond length is 2.52 Å. The Fe(7)-Fe(14) bond length is 2.44 Å. The Fe(7)-Si(1) bond length is 2.42 Å. There is one shorter (2.73 Å) and one longer (2.95 Å) Fe(7)-Si(2) bond length. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Er(2), one Fe(12), one Fe(15), one Fe(16), one Fe(3), one Fe(5), one Fe(9), two equivalent Fe(2), and two equivalent Si(3) atoms. The Fe(8)-Fe(12) bond length is 2.51 Å. The Fe(8)-Fe(15) bond length is 2.43 Å. The Fe(8)-Fe(16) bond length is 2.43 Å. The Fe(8)-Fe(9) bond length is 2.50 Å. There is one shorter (2.81 Å) and one longer (2.82 Å) Fe(8)-Si(3) bond length. In the ninth Fe site, Fe(9) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(12), one Fe(13), one Fe(16), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(8), and two equivalent Si(3) atoms. The Fe(9)-Fe(12) bond length is 2.51 Å. The Fe(9)-Fe(13) bond length is 2.42 Å. The Fe(9)-Fe(16) bond length is 2.43 Å. There is one shorter (2.81 Å) and one longer (2.82 Å) Fe(9)-Si(3) bond length. In the tenth Fe site, Fe(10) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(1), one Fe(11), one Fe(13), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Si(1), and two equivalent Si(2) atoms. The Fe(10)-Fe(11) bond length is 2.52 Å. The Fe(10)-Fe(13) bond length is 2.44 Å. The Fe(10)-Si(1) bond length is 2.41 Å. There is one shorter (2.73 Å) and one longer (2.95 Å) Fe(10)-Si(2) bond length. In the eleventh Fe site, Fe(11) is bonded to one Er(1), one Er(2), one Fe(1), one Fe(10), one Fe(13), one Fe(14), one Fe(4), one Fe(5), one Fe(6), one Fe(7), and two equivalent Si(2) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(13)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(1)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(13)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(15)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(13)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, faces with three equivalent Fe(1)Er3Fe7Si2 cuboctahedra, and faces with three equivalent Fe(6)Er3Fe8Si cuboctahedra. The Fe(11)-Fe(13) bond length is 2.43 Å. The Fe(11)-Fe(14) bond length is 2.42 Å. Both Fe(11)-Si(2) bond lengths are 2.74 Å. In the twelfth Fe site, Fe(12) is bonded in a 12-coordinate geometry to one Er(1), one Er(2), one Fe(13), one Fe(15), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(8), one Fe(9), and two equivalent Si(3) atoms. The Fe(12)-Fe(13) bond length is 2.42 Å. The Fe(12)-Fe(15) bond length is 2.43 Å. There is one shorter (2.77 Å) and one longer (2.78 Å) Fe(12)-Si(3) bond length. In the thirteenth Fe site, Fe(13) is bonded to one Er(1), one Er(2), one Fe(10), one Fe(11), one Fe(12), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(9), one Si(2), and one Si(3) atom to form distorted FeEr2Fe8Si2 cuboctahedra that share  a cornercorner with one Fe(11)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(14)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(15)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(16)Er2Fe8Si2 cuboctahedra,  a cornercorner with one Fe(4)Er3Fe7Si2 cuboctahedra,  a cornercorner with one Fe(3)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(5)Er3Fe8Si cuboctahedra,  a cornercorner with one Fe(6)Er3Fe8Si cuboctahedra, corners with three equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with three equivalent Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(11)Er2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(1)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Er3Fe7Si2 cuboctahedra,  an edgeedge with one Fe(2)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(3)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(5)Er3Fe8Si cuboctahedra,  an edgeedge with one Fe(6)Er3Fe8Si cuboctahedra,  a faceface with one Fe(11)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(14)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(15)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(16)Er2Fe8Si2 cuboctahedra,  a faceface with one Fe(1)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(4)Er3Fe7Si2 cuboctahedra,  a faceface with one Fe(2)Er3Fe8Si cuboctahedra,  a faceface with one Fe(3)Er3Fe8Si cuboctahedra,  a faceface with one Fe(5)Er3Fe8Si cuboctahedra, and  a faceface with one Fe(6)Er3Fe8Si cuboctahedra. The Fe(13)-Si(2) bond length is 2.47 Å. The Fe(13)-Si(3) bond length is 2.53 Å. In the fourteenth Fe site, Fe(14) is bonded to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(11), two equivalent Fe(6), two equivalent Fe(7), and two equivalent Si(2) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(2)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(6)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, faces with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, and faces with two equivalent Fe(6)Er3Fe8Si cuboctahedra. Both Fe(14)-Si(2) bond lengths are 2.47 Å. In the fifteenth Fe site, Fe(15) is bonded to two equivalent Er(2), two equivalent Fe(12), two equivalent Fe(2), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(3) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, edges with two equivalent Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(3)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(6)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(16)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. Both Fe(15)-Si(3) bond lengths are 2.52 Å. In the sixteenth Fe site, Fe(16) is bonded to two equivalent Er(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(8), two equivalent Fe(9), and two equivalent Si(3) atoms to form distorted FeEr2Fe8Si2 cuboctahedra that share corners with two equivalent Fe(11)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, corners with two equivalent Fe(1)Er3Fe7Si2 cuboctahedra, corners with two equivalent Fe(3)Er3Fe8Si cuboctahedra, corners with two equivalent Fe(5)Er3Fe8Si cuboctahedra, corners with four equivalent Fe(6)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(4)Er3Fe7Si2 cuboctahedra, edges with two equivalent Fe(2)Er3Fe8Si cuboctahedra, edges with two equivalent Fe(5)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(13)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(15)Er2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Er3Fe8Si cuboctahedra, faces with two equivalent Fe(3)Er3Fe8Si cuboctahedra, and faces with two equivalent Fe(5)Er3Fe8Si cuboctahedra. Both Fe(16)-Si(3) bond lengths are 2.54 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Fe(1), two equivalent Fe(10), two equivalent Fe(4), two equivalent Fe(7), and two equivalent Si(2) atoms. Both Si(1)-Si(2) bond lengths are 2.68 Å. In the second Si site, Si(2) is bonded in a 14-coordinate geometry to one Er(1), one Fe(1), one Fe(13), one Fe(14), one Fe(4), one Fe(6), two equivalent Fe(10), two equivalent Fe(11), two equivalent Fe(7), one Si(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.48 Å. In the third Si site, Si(3) is bonded in a 14-coordinate geometry to one Er(2), one Fe(13), one Fe(15), one Fe(16), one Fe(2), one Fe(3), one Fe(5), two equivalent Fe(12), two equivalent Fe(8), two equivalent Fe(9), and one Si(3) atom. The Si(3)-Si(3) bond length is 2.51 Å.