Tb3NiSi3 crystallizes in the orthorhombic Imm2 space group. There are three inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 7-coordinate geometry to one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. In the second Tb site, Tb(2) is bonded in a 7-coordinate geometry to two equivalent Ni(1), one Si(2), and four equivalent Si(1) atoms. In the third Tb site, Tb(3) is bonded to four equivalent Ni(1), two equivalent Si(1), two equivalent Si(2), and four equivalent Si(3) atoms to form a mixture of edge and face-sharing TbSi8Ni4 cuboctahedra. Ni(1) is bonded in a 9-coordinate geometry to two equivalent Tb(2), four equivalent Tb(3), one Si(3), and two equivalent Si(1) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Tb(1), two equivalent Tb(3), four equivalent Tb(2), and two equivalent Ni(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Tb(2), two equivalent Tb(3), four equivalent Tb(1), and two equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Tb(1), four equivalent Tb(3), one Ni(1), and two equivalent Si(2) atoms.
Tb3NiSi3 crystallizes in the orthorhombic Imm2 space group. There are three inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 7-coordinate geometry to one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. The Tb(1)-Si(1) bond length is 3.10 Å. Both Tb(1)-Si(3) bond lengths are 3.02 Å. All Tb(1)-Si(2) bond lengths are 2.95 Å. In the second Tb site, Tb(2) is bonded in a 7-coordinate geometry to two equivalent Ni(1), one Si(2), and four equivalent Si(1) atoms. Both Tb(2)-Ni(1) bond lengths are 2.88 Å. The Tb(2)-Si(2) bond length is 3.05 Å. All Tb(2)-Si(1) bond lengths are 2.96 Å. In the third Tb site, Tb(3) is bonded to four equivalent Ni(1), two equivalent Si(1), two equivalent Si(2), and four equivalent Si(3) atoms to form a mixture of edge and face-sharing TbSi8Ni4 cuboctahedra. All Tb(3)-Ni(1) bond lengths are 3.09 Å. Both Tb(3)-Si(1) bond lengths are 3.17 Å. Both Tb(3)-Si(2) bond lengths are 3.26 Å. All Tb(3)-Si(3) bond lengths are 3.05 Å. Ni(1) is bonded in a 9-coordinate geometry to two equivalent Tb(2), four equivalent Tb(3), one Si(3), and two equivalent Si(1) atoms. The Ni(1)-Si(3) bond length is 2.22 Å. Both Ni(1)-Si(1) bond lengths are 2.32 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Tb(1), two equivalent Tb(3), four equivalent Tb(2), and two equivalent Ni(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Tb(2), two equivalent Tb(3), four equivalent Tb(1), and two equivalent Si(3) atoms. Both Si(2)-Si(3) bond lengths are 2.46 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Tb(1), four equivalent Tb(3), one Ni(1), and two equivalent Si(2) atoms.