YFe6Sn6 crystallizes in the orthorhombic Immm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent Fe(1), eight equivalent Fe(4), two equivalent Sn(1), two equivalent Sn(3), and four equivalent Sn(5) atoms to form distorted YFe12Sn8 hexagonal bipyramids that share faces with four equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids. In the second Y site, Y(2) is bonded to four equivalent Fe(2), four equivalent Fe(3), four equivalent Fe(4), one Sn(5), one Sn(7), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(8) atoms to form distorted YFe12Sn8 hexagonal bipyramids that share corners with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids, faces with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, faces with six equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Y(2)Fe12Sn8 hexagonal bipyramids. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Y(1), four equivalent Fe(4), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(5) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(1)Y2Fe4Sn6 cuboctahedra,  a faceface with one Fe(1)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Y(2)Fe12Sn8 hexagonal bipyramids. In the second Fe site, Fe(2) is bonded to two equivalent Y(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Sn(4), two equivalent Sn(7), and two equivalent Sn(8) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, and faces with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids. In the third Fe site, Fe(3) is bonded to two equivalent Y(2), two equivalent Fe(2), two equivalent Fe(4), one Sn(3), one Sn(4), one Sn(6), one Sn(7), and two equivalent Sn(8) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(3)Y2Fe4Sn6 cuboctahedra,  a faceface with one Fe(3)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra,  a faceface with one Y(1)Fe12Sn8 hexagonal bipyramid, and faces with three equivalent Y(2)Fe12Sn8 hexagonal bipyramids. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to one Y(1), one Y(2), one Fe(1), one Fe(3), two equivalent Fe(4), one Sn(1), one Sn(2), one Sn(3), one Sn(5), one Sn(6), and one Sn(8) atom. There are eight inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 8-coordinate geometry to one Y(1), two equivalent Fe(1), four equivalent Fe(4), and one Sn(1) atom. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent Fe(1) and four equivalent Fe(4) atoms. In the third Sn site, Sn(3) is bonded in a 9-coordinate geometry to one Y(1), two equivalent Y(2), two equivalent Fe(3), and four equivalent Fe(4) atoms. In the fourth Sn site, Sn(4) is bonded in a 8-coordinate geometry to two equivalent Y(2), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Y(2), two equivalent Y(1), two equivalent Fe(1), and four equivalent Fe(4) atoms. In the sixth Sn site, Sn(6) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(4) atoms. In the seventh Sn site, Sn(7) is bonded in a 7-coordinate geometry to one Y(2), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the eighth Sn site, Sn(8) is bonded in a 8-coordinate geometry to one Y(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and one Sn(8) atom.
YFe6Sn6 crystallizes in the orthorhombic Immm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent Fe(1), eight equivalent Fe(4), two equivalent Sn(1), two equivalent Sn(3), and four equivalent Sn(5) atoms to form distorted YFe12Sn8 hexagonal bipyramids that share faces with four equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids. All Y(1)-Fe(1) bond lengths are 3.49 Å. All Y(1)-Fe(4) bond lengths are 3.51 Å. Both Y(1)-Sn(1) bond lengths are 3.02 Å. Both Y(1)-Sn(3) bond lengths are 3.17 Å. All Y(1)-Sn(5) bond lengths are 3.13 Å. In the second Y site, Y(2) is bonded to four equivalent Fe(2), four equivalent Fe(3), four equivalent Fe(4), one Sn(5), one Sn(7), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(8) atoms to form distorted YFe12Sn8 hexagonal bipyramids that share corners with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids, faces with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, faces with six equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Y(2)Fe12Sn8 hexagonal bipyramids. All Y(2)-Fe(2) bond lengths are 3.49 Å. All Y(2)-Fe(3) bond lengths are 3.50 Å. All Y(2)-Fe(4) bond lengths are 3.53 Å. The Y(2)-Sn(5) bond length is 3.17 Å. The Y(2)-Sn(7) bond length is 3.16 Å. Both Y(2)-Sn(3) bond lengths are 3.13 Å. Both Y(2)-Sn(4) bond lengths are 3.12 Å. Both Y(2)-Sn(8) bond lengths are 3.03 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Y(1), four equivalent Fe(4), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(5) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(1)Y2Fe4Sn6 cuboctahedra,  a faceface with one Fe(1)Y2Fe4Sn6 cuboctahedra, faces with two equivalent Y(1)Fe12Sn8 hexagonal bipyramids, and faces with two equivalent Y(2)Fe12Sn8 hexagonal bipyramids. All Fe(1)-Fe(4) bond lengths are 2.72 Å. Both Fe(1)-Sn(1) bond lengths are 2.82 Å. Both Fe(1)-Sn(2) bond lengths are 2.77 Å. Both Fe(1)-Sn(5) bond lengths are 2.72 Å. In the second Fe site, Fe(2) is bonded to two equivalent Y(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Sn(4), two equivalent Sn(7), and two equivalent Sn(8) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, and faces with four equivalent Y(2)Fe12Sn8 hexagonal bipyramids. Both Fe(2)-Fe(2) bond lengths are 2.70 Å. Both Fe(2)-Fe(3) bond lengths are 2.72 Å. Both Fe(2)-Sn(4) bond lengths are 2.73 Å. Both Fe(2)-Sn(7) bond lengths are 2.76 Å. Both Fe(2)-Sn(8) bond lengths are 2.83 Å. In the third Fe site, Fe(3) is bonded to two equivalent Y(2), two equivalent Fe(2), two equivalent Fe(4), one Sn(3), one Sn(4), one Sn(6), one Sn(7), and two equivalent Sn(8) atoms to form distorted FeY2Fe4Sn6 cuboctahedra that share corners with two equivalent Fe(1)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Y2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Y2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(3)Y2Fe4Sn6 cuboctahedra,  a faceface with one Fe(3)Y2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Y2Fe4Sn6 cuboctahedra,  a faceface with one Y(1)Fe12Sn8 hexagonal bipyramid, and faces with three equivalent Y(2)Fe12Sn8 hexagonal bipyramids. Both Fe(3)-Fe(4) bond lengths are 2.70 Å. The Fe(3)-Sn(3) bond length is 2.71 Å. The Fe(3)-Sn(4) bond length is 2.75 Å. The Fe(3)-Sn(6) bond length is 2.77 Å. The Fe(3)-Sn(7) bond length is 2.72 Å. Both Fe(3)-Sn(8) bond lengths are 2.82 Å. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to one Y(1), one Y(2), one Fe(1), one Fe(3), two equivalent Fe(4), one Sn(1), one Sn(2), one Sn(3), one Sn(5), one Sn(6), and one Sn(8) atom. There is one shorter (2.70 Å) and one longer (2.71 Å) Fe(4)-Fe(4) bond length. The Fe(4)-Sn(1) bond length is 2.83 Å. The Fe(4)-Sn(2) bond length is 2.77 Å. The Fe(4)-Sn(3) bond length is 2.72 Å. The Fe(4)-Sn(5) bond length is 2.71 Å. The Fe(4)-Sn(6) bond length is 2.75 Å. The Fe(4)-Sn(8) bond length is 2.82 Å. There are eight inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 8-coordinate geometry to one Y(1), two equivalent Fe(1), four equivalent Fe(4), and one Sn(1) atom. The Sn(1)-Sn(1) bond length is 2.95 Å. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent Fe(1) and four equivalent Fe(4) atoms. In the third Sn site, Sn(3) is bonded in a 9-coordinate geometry to one Y(1), two equivalent Y(2), two equivalent Fe(3), and four equivalent Fe(4) atoms. In the fourth Sn site, Sn(4) is bonded in a 8-coordinate geometry to two equivalent Y(2), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Y(2), two equivalent Y(1), two equivalent Fe(1), and four equivalent Fe(4) atoms. In the sixth Sn site, Sn(6) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(4) atoms. In the seventh Sn site, Sn(7) is bonded in a 7-coordinate geometry to one Y(2), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the eighth Sn site, Sn(8) is bonded in a 8-coordinate geometry to one Y(2), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and one Sn(8) atom. The Sn(8)-Sn(8) bond length is 2.94 Å.