Th3Ce3Si4 crystallizes in the monoclinic Pm space group. There are three inequivalent Th sites. In the first Th site, Th(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Th site, Th(2) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. In the third Th site, Th(3) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a distorted square co-planar geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the second Ce site, Ce(2) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. In the third Ce site, Ce(3) is bonded in a distorted hexagonal planar geometry to two equivalent Si(2), two equivalent Si(3), and two equivalent Si(4) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(2), two equivalent Th(3), one Ce(1), one Ce(2), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Th(2), two equivalent Th(3), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(3), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(2), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(3) atom.
Th3Ce3Si4 crystallizes in the monoclinic Pm space group. There are three inequivalent Th sites. In the first Th site, Th(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. Both Th(1)-Si(1) bond lengths are 3.11 Å. Both Th(1)-Si(3) bond lengths are 3.14 Å. Both Th(1)-Si(4) bond lengths are 3.15 Å. In the second Th site, Th(2) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. Both Th(2)-Si(1) bond lengths are 3.14 Å. Both Th(2)-Si(2) bond lengths are 3.14 Å. Both Th(2)-Si(4) bond lengths are 3.11 Å. In the third Th site, Th(3) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. Both Th(3)-Si(1) bond lengths are 3.14 Å. Both Th(3)-Si(2) bond lengths are 3.13 Å. Both Th(3)-Si(3) bond lengths are 3.11 Å. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a distorted square co-planar geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. The Ce(1)-Si(1) bond length is 3.15 Å. The Ce(1)-Si(2) bond length is 3.14 Å. The Ce(1)-Si(3) bond length is 3.15 Å. The Ce(1)-Si(4) bond length is 3.18 Å. In the second Ce site, Ce(2) is bonded in a distorted rectangular see-saw-like geometry to one Si(1), one Si(2), one Si(3), and one Si(4) atom. The Ce(2)-Si(1) bond length is 3.19 Å. The Ce(2)-Si(2) bond length is 3.17 Å. The Ce(2)-Si(3) bond length is 3.18 Å. The Ce(2)-Si(4) bond length is 3.18 Å. In the third Ce site, Ce(3) is bonded in a distorted hexagonal planar geometry to two equivalent Si(2), two equivalent Si(3), and two equivalent Si(4) atoms. Both Ce(3)-Si(2) bond lengths are 3.15 Å. Both Ce(3)-Si(3) bond lengths are 3.16 Å. Both Ce(3)-Si(4) bond lengths are 3.15 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(2), two equivalent Th(3), one Ce(1), one Ce(2), and one Si(2) atom. The Si(1)-Si(2) bond length is 2.47 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Th(2), two equivalent Th(3), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(1) atom. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(3), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(4) atom. The Si(3)-Si(4) bond length is 2.46 Å. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Th(1), two equivalent Th(2), one Ce(1), one Ce(2), two equivalent Ce(3), and one Si(3) atom.