Tm2Co3Si5 crystallizes in the orthorhombic Ibam space group. Tm(1) is bonded in a 13-coordinate geometry to two equivalent Co(2), three equivalent Co(1), two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a 8-coordinate geometry to three equivalent Tm(1), one Si(3), two equivalent Si(1), and two equivalent Si(2) atoms. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to four equivalent Tm(1), two equivalent Co(2), two equivalent Si(1), and four equivalent Si(3) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to four equivalent Tm(1), one Co(2), two equivalent Co(1), two equivalent Si(1), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Tm(1) and four equivalent Co(1) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one Co(1), two equivalent Co(2), and two equivalent Si(1) atoms.
Tm2Co3Si5 crystallizes in the orthorhombic Ibam space group. Tm(1) is bonded in a 13-coordinate geometry to two equivalent Co(2), three equivalent Co(1), two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms. Both Tm(1)-Co(2) bond lengths are 3.23 Å. There is one shorter (2.93 Å) and two longer (2.97 Å) Tm(1)-Co(1) bond lengths. There is one shorter (2.98 Å) and one longer (2.99 Å) Tm(1)-Si(2) bond length. There are two shorter (3.01 Å) and two longer (3.03 Å) Tm(1)-Si(1) bond lengths. There are a spread of Tm(1)-Si(3) bond distances ranging from 2.81-3.04 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a 8-coordinate geometry to three equivalent Tm(1), one Si(3), two equivalent Si(1), and two equivalent Si(2) atoms. The Co(1)-Si(3) bond length is 2.23 Å. Both Co(1)-Si(1) bond lengths are 2.28 Å. Both Co(1)-Si(2) bond lengths are 2.30 Å. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to four equivalent Tm(1), two equivalent Co(2), two equivalent Si(1), and four equivalent Si(3) atoms. Both Co(2)-Co(2) bond lengths are 2.73 Å. Both Co(2)-Si(1) bond lengths are 2.51 Å. All Co(2)-Si(3) bond lengths are 2.31 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to four equivalent Tm(1), one Co(2), two equivalent Co(1), two equivalent Si(1), and two equivalent Si(3) atoms. Both Si(1)-Si(1) bond lengths are 2.73 Å. Both Si(1)-Si(3) bond lengths are 2.46 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Tm(1) and four equivalent Co(1) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one Co(1), two equivalent Co(2), and two equivalent Si(1) atoms.