TbFe6Sn6 crystallizes in the orthorhombic Cmcm space group. Tb(1) is bonded to four equivalent Fe(1), four equivalent Fe(2), four equivalent Fe(3), one Sn(4), two equivalent Sn(3), two equivalent Sn(5), and three equivalent Sn(1) atoms to form distorted TbFe12Sn8 hexagonal bipyramids that share corners with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids, faces with eight equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Tb(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, faces with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. In the second Fe site, Fe(2) is bonded to two equivalent Tb(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with three equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. In the third Fe site, Fe(3) is bonded to two equivalent Tb(1), two equivalent Fe(1), two equivalent Fe(2), one Sn(1), one Sn(2), one Sn(3), one Sn(4), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra,  a faceface with one Fe(3)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. There are five inequivalent Sn sites. In the first Sn site, Sn(3) is bonded in a 8-coordinate geometry to two equivalent Tb(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the second Sn site, Sn(4) is bonded in a 7-coordinate geometry to one Tb(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the third Sn site, Sn(5) is bonded in a 8-coordinate geometry to one Tb(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and one Sn(5) atom. In the fourth Sn site, Sn(1) is bonded in a 9-coordinate geometry to three equivalent Tb(1), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(2) atoms.
TbFe6Sn6 crystallizes in the orthorhombic Cmcm space group. Tb(1) is bonded to four equivalent Fe(1), four equivalent Fe(2), four equivalent Fe(3), one Sn(4), two equivalent Sn(3), two equivalent Sn(5), and three equivalent Sn(1) atoms to form distorted TbFe12Sn8 hexagonal bipyramids that share corners with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids, faces with eight equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with eight equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. All Tb(1)-Fe(1) bond lengths are 3.48 Å. All Tb(1)-Fe(2) bond lengths are 3.53 Å. All Tb(1)-Fe(3) bond lengths are 3.51 Å. The Tb(1)-Sn(4) bond length is 3.14 Å. Both Tb(1)-Sn(3) bond lengths are 3.13 Å. Both Tb(1)-Sn(5) bond lengths are 3.03 Å. There are two shorter (3.16 Å) and one longer (3.18 Å) Tb(1)-Sn(1) bond length. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Tb(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Sn(3), two equivalent Sn(4), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, faces with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. Both Fe(1)-Fe(1) bond lengths are 2.72 Å. Both Fe(1)-Fe(3) bond lengths are 2.71 Å. Both Fe(1)-Sn(3) bond lengths are 2.72 Å. Both Fe(1)-Sn(4) bond lengths are 2.76 Å. Both Fe(1)-Sn(5) bond lengths are 2.83 Å. In the second Fe site, Fe(2) is bonded to two equivalent Tb(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with three equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. Both Fe(2)-Fe(2) bond lengths are 2.72 Å. Both Fe(2)-Fe(3) bond lengths are 2.71 Å. Both Fe(2)-Sn(1) bond lengths are 2.71 Å. Both Fe(2)-Sn(2) bond lengths are 2.76 Å. Both Fe(2)-Sn(5) bond lengths are 2.82 Å. In the third Fe site, Fe(3) is bonded to two equivalent Tb(1), two equivalent Fe(1), two equivalent Fe(2), one Sn(1), one Sn(2), one Sn(3), one Sn(4), and two equivalent Sn(5) atoms to form distorted FeTb2Fe4Sn6 cuboctahedra that share corners with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, corners with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, corners with six equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, edges with two equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, edges with three equivalent Fe(3)Tb2Fe4Sn6 cuboctahedra,  a faceface with one Fe(3)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(1)Tb2Fe4Sn6 cuboctahedra, faces with four equivalent Fe(2)Tb2Fe4Sn6 cuboctahedra, and faces with four equivalent Tb(1)Fe12Sn8 hexagonal bipyramids. The Fe(3)-Sn(1) bond length is 2.71 Å. The Fe(3)-Sn(2) bond length is 2.77 Å. The Fe(3)-Sn(3) bond length is 2.74 Å. The Fe(3)-Sn(4) bond length is 2.72 Å. Both Fe(3)-Sn(5) bond lengths are 2.83 Å. There are five inequivalent Sn sites. In the first Sn site, Sn(3) is bonded in a 8-coordinate geometry to two equivalent Tb(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the second Sn site, Sn(4) is bonded in a 7-coordinate geometry to one Tb(1), two equivalent Fe(3), and four equivalent Fe(1) atoms. In the third Sn site, Sn(5) is bonded in a 8-coordinate geometry to one Tb(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and one Sn(5) atom. The Sn(5)-Sn(5) bond length is 2.93 Å. In the fourth Sn site, Sn(1) is bonded in a 9-coordinate geometry to three equivalent Tb(1), two equivalent Fe(3), and four equivalent Fe(2) atoms. In the fifth Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent Fe(3) and four equivalent Fe(2) atoms.