Tb2Si3 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 10-coordinate geometry to two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms. In the second Tb site, Tb(2) is bonded in a 8-coordinate geometry to two equivalent Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Tb(2), four equivalent Tb(1), one Si(3), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Tb(1), four equivalent Tb(2), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to two equivalent Tb(2), four equivalent Tb(1), and one Si(1) atom.
Tb2Si3 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 10-coordinate geometry to two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms. Both Tb(1)-Si(2) bond lengths are 3.13 Å. All Tb(1)-Si(1) bond lengths are 2.98 Å. All Tb(1)-Si(3) bond lengths are 3.08 Å. In the second Tb site, Tb(2) is bonded in a 8-coordinate geometry to two equivalent Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. Both Tb(2)-Si(1) bond lengths are 3.11 Å. Both Tb(2)-Si(3) bond lengths are 2.95 Å. All Tb(2)-Si(2) bond lengths are 2.97 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Tb(2), four equivalent Tb(1), one Si(3), and two equivalent Si(2) atoms. The Si(1)-Si(3) bond length is 2.31 Å. Both Si(1)-Si(2) bond lengths are 2.36 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Tb(1), four equivalent Tb(2), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 7-coordinate geometry to two equivalent Tb(2), four equivalent Tb(1), and one Si(1) atom.