Tm3NiSi3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 11-coordinate geometry to four equivalent Ni(1), two equivalent Si(1), and five equivalent Si(3) atoms. In the second Tm site, Tm(2) is bonded in a 7-coordinate geometry to two equivalent Si(1) and five equivalent Si(2) atoms. In the third Tm site, Tm(3) is bonded in a 8-coordinate geometry to two equivalent Ni(1), one Si(3), two equivalent Si(2), and three equivalent Si(1) atoms. Ni(1) is bonded in a 10-coordinate geometry to two equivalent Tm(3), four equivalent Tm(1), one Si(1), and three equivalent Si(3) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Tm(1), two equivalent Tm(2), three equivalent Tm(3), one Ni(1), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Tm(3), five equivalent Tm(2), one Si(1), and one Si(2) atom. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Tm(3), five equivalent Tm(1), three equivalent Ni(1), and one Si(3) atom.
Tm3NiSi3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 11-coordinate geometry to four equivalent Ni(1), two equivalent Si(1), and five equivalent Si(3) atoms. There are a spread of Tm(1)-Ni(1) bond distances ranging from 2.96-2.99 Å. Both Tm(1)-Si(1) bond lengths are 2.86 Å. There are a spread of Tm(1)-Si(3) bond distances ranging from 2.91-3.16 Å. In the second Tm site, Tm(2) is bonded in a 7-coordinate geometry to two equivalent Si(1) and five equivalent Si(2) atoms. Both Tm(2)-Si(1) bond lengths are 2.95 Å. There are a spread of Tm(2)-Si(2) bond distances ranging from 2.87-3.03 Å. In the third Tm site, Tm(3) is bonded in a 8-coordinate geometry to two equivalent Ni(1), one Si(3), two equivalent Si(2), and three equivalent Si(1) atoms. Both Tm(3)-Ni(1) bond lengths are 3.11 Å. The Tm(3)-Si(3) bond length is 2.86 Å. Both Tm(3)-Si(2) bond lengths are 2.87 Å. There are two shorter (2.94 Å) and one longer (3.00 Å) Tm(3)-Si(1) bond length. Ni(1) is bonded in a 10-coordinate geometry to two equivalent Tm(3), four equivalent Tm(1), one Si(1), and three equivalent Si(3) atoms. The Ni(1)-Si(1) bond length is 2.43 Å. There are two shorter (2.36 Å) and one longer (2.50 Å) Ni(1)-Si(3) bond length. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Tm(1), two equivalent Tm(2), three equivalent Tm(3), one Ni(1), 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 Tm(3), five equivalent Tm(2), one Si(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.51 Å. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Tm(3), five equivalent Tm(1), three equivalent Ni(1), and one Si(3) atom. The Si(3)-Si(3) bond length is 2.62 Å.