TbNdFe17 crystallizes in the trigonal R3m space group. Tb(1) is bonded in a 19-coordinate geometry to one Fe(6), three equivalent Fe(2), three equivalent Fe(4), six equivalent Fe(1), and six equivalent Fe(3) atoms. Nd(1) is bonded in a 19-coordinate geometry to one Fe(5), three equivalent Fe(1), three equivalent Fe(4), six equivalent Fe(2), and six equivalent Fe(3) atoms. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Tb(1), one Nd(1), one Fe(6), two equivalent Fe(2), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeTb2NdFe9 cuboctahedra that share corners with two equivalent Fe(1)Tb2NdFe9 cuboctahedra, corners with five equivalent Fe(4)TbNdFe10 cuboctahedra, corners with eight equivalent Fe(2)TbNd2Fe9 cuboctahedra,  an edgeedge with one Fe(2)TbNd2Fe9 cuboctahedra, edges with three equivalent Fe(4)TbNdFe10 cuboctahedra, edges with four equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(4)TbNdFe10 cuboctahedra, and faces with four equivalent Fe(1)Tb2NdFe9 cuboctahedra. In the second Fe site, Fe(2) is bonded to one Tb(1), two equivalent Nd(1), one Fe(5), two equivalent Fe(1), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeTbNd2Fe9 cuboctahedra that share corners with two equivalent Fe(2)TbNd2Fe9 cuboctahedra, corners with five equivalent Fe(4)TbNdFe10 cuboctahedra, corners with eight equivalent Fe(1)Tb2NdFe9 cuboctahedra,  an edgeedge with one Fe(1)Tb2NdFe9 cuboctahedra, edges with three equivalent Fe(4)TbNdFe10 cuboctahedra, edges with four equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(4)TbNdFe10 cuboctahedra, and faces with four equivalent Fe(2)TbNd2Fe9 cuboctahedra. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to one Tb(1), one Nd(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Fe(4) atoms. In the fourth Fe site, Fe(4) is bonded to one Tb(1), one Nd(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), and four equivalent Fe(3) atoms to form FeTbNdFe10 cuboctahedra that share corners with four equivalent Fe(4)TbNdFe10 cuboctahedra, corners with five equivalent Fe(1)Tb2NdFe9 cuboctahedra, corners with five equivalent Fe(2)TbNd2Fe9 cuboctahedra, edges with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, edges with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, and faces with four equivalent Fe(4)TbNdFe10 cuboctahedra. In the fifth Fe site, Fe(5) is bonded in a 14-coordinate geometry to one Nd(1), one Fe(6), three equivalent Fe(2), three equivalent Fe(4), and six equivalent Fe(3) atoms. In the sixth Fe site, Fe(6) is bonded in a 14-coordinate geometry to one Tb(1), one Fe(5), three equivalent Fe(1), three equivalent Fe(4), and six equivalent Fe(3) atoms.
TbNdFe17 crystallizes in the trigonal R3m space group. Tb(1) is bonded in a 19-coordinate geometry to one Fe(6), three equivalent Fe(2), three equivalent Fe(4), six equivalent Fe(1), and six equivalent Fe(3) atoms. The Tb(1)-Fe(6) bond length is 3.14 Å. All Tb(1)-Fe(2) bond lengths are 3.07 Å. All Tb(1)-Fe(4) bond lengths are 3.26 Å. There are three shorter (3.17 Å) and three longer (3.21 Å) Tb(1)-Fe(1) bond lengths. All Tb(1)-Fe(3) bond lengths are 3.00 Å. Nd(1) is bonded in a 19-coordinate geometry to one Fe(5), three equivalent Fe(1), three equivalent Fe(4), six equivalent Fe(2), and six equivalent Fe(3) atoms. The Nd(1)-Fe(5) bond length is 3.16 Å. All Nd(1)-Fe(1) bond lengths are 3.07 Å. All Nd(1)-Fe(4) bond lengths are 3.29 Å. There are three shorter (3.18 Å) and three longer (3.20 Å) Nd(1)-Fe(2) bond lengths. All Nd(1)-Fe(3) bond lengths are 3.01 Å. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Tb(1), one Nd(1), one Fe(6), two equivalent Fe(2), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeTb2NdFe9 cuboctahedra that share corners with two equivalent Fe(1)Tb2NdFe9 cuboctahedra, corners with five equivalent Fe(4)TbNdFe10 cuboctahedra, corners with eight equivalent Fe(2)TbNd2Fe9 cuboctahedra,  an edgeedge with one Fe(2)TbNd2Fe9 cuboctahedra, edges with three equivalent Fe(4)TbNdFe10 cuboctahedra, edges with four equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(4)TbNdFe10 cuboctahedra, and faces with four equivalent Fe(1)Tb2NdFe9 cuboctahedra. The Fe(1)-Fe(6) bond length is 2.61 Å. Both Fe(1)-Fe(2) bond lengths are 2.48 Å. Both Fe(1)-Fe(4) bond lengths are 2.41 Å. There are two shorter (2.50 Å) and two longer (2.64 Å) Fe(1)-Fe(3) bond lengths. In the second Fe site, Fe(2) is bonded to one Tb(1), two equivalent Nd(1), one Fe(5), two equivalent Fe(1), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeTbNd2Fe9 cuboctahedra that share corners with two equivalent Fe(2)TbNd2Fe9 cuboctahedra, corners with five equivalent Fe(4)TbNdFe10 cuboctahedra, corners with eight equivalent Fe(1)Tb2NdFe9 cuboctahedra,  an edgeedge with one Fe(1)Tb2NdFe9 cuboctahedra, edges with three equivalent Fe(4)TbNdFe10 cuboctahedra, edges with four equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(4)TbNdFe10 cuboctahedra, and faces with four equivalent Fe(2)TbNd2Fe9 cuboctahedra. The Fe(2)-Fe(5) bond length is 2.63 Å. Both Fe(2)-Fe(4) bond lengths are 2.42 Å. There are two shorter (2.52 Å) and two longer (2.63 Å) Fe(2)-Fe(3) bond lengths. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to one Tb(1), one Nd(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Fe(4) atoms. The Fe(3)-Fe(5) bond length is 2.68 Å. The Fe(3)-Fe(6) bond length is 2.68 Å. There is one shorter (2.42 Å) and one longer (2.45 Å) Fe(3)-Fe(3) bond length. There is one shorter (2.41 Å) and one longer (2.43 Å) Fe(3)-Fe(4) bond length. In the fourth Fe site, Fe(4) is bonded to one Tb(1), one Nd(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), and four equivalent Fe(3) atoms to form FeTbNdFe10 cuboctahedra that share corners with four equivalent Fe(4)TbNdFe10 cuboctahedra, corners with five equivalent Fe(1)Tb2NdFe9 cuboctahedra, corners with five equivalent Fe(2)TbNd2Fe9 cuboctahedra, edges with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, edges with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, faces with three equivalent Fe(1)Tb2NdFe9 cuboctahedra, faces with three equivalent Fe(2)TbNd2Fe9 cuboctahedra, and faces with four equivalent Fe(4)TbNdFe10 cuboctahedra. The Fe(4)-Fe(5) bond length is 2.62 Å. The Fe(4)-Fe(6) bond length is 2.60 Å. In the fifth Fe site, Fe(5) is bonded in a 14-coordinate geometry to one Nd(1), one Fe(6), three equivalent Fe(2), three equivalent Fe(4), and six equivalent Fe(3) atoms. The Fe(5)-Fe(6) bond length is 2.22 Å. In the sixth Fe site, Fe(6) is bonded in a 14-coordinate geometry to one Tb(1), one Fe(5), three equivalent Fe(1), three equivalent Fe(4), and six equivalent Fe(3) atoms.