ThCoSi3 crystallizes in the tetragonal I4mm space group. Th(1) is bonded in a 17-coordinate geometry to five equivalent Co(1), four equivalent Si(1), and eight equivalent Si(2) atoms. Co(1) is bonded in a 5-coordinate geometry to five equivalent Th(1), one Si(1), and four equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent Th(1), one Co(1), and four equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Th(1), two equivalent Co(1), and two equivalent Si(1) atoms.
ThCoSi3 crystallizes in the tetragonal I4mm space group. Th(1) is bonded in a 17-coordinate geometry to five equivalent Co(1), four equivalent Si(1), and eight equivalent Si(2) atoms. There is one shorter (3.21 Å) and four longer (3.30 Å) Th(1)-Co(1) bond lengths. All Th(1)-Si(1) bond lengths are 3.04 Å. There are four shorter (3.08 Å) and four longer (3.21 Å) Th(1)-Si(2) bond lengths. Co(1) is bonded in a 5-coordinate geometry to five equivalent Th(1), one Si(1), and four equivalent Si(2) atoms. The Co(1)-Si(1) bond length is 2.27 Å. All Co(1)-Si(2) bond lengths are 2.28 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent Th(1), one Co(1), and four equivalent Si(2) atoms. All Si(1)-Si(2) bond lengths are 2.57 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Th(1), two equivalent Co(1), and two equivalent Si(1) atoms.