Tb2Co3Si5 crystallizes in the orthorhombic Ibam space group. Tb(1) is bonded in a 13-coordinate geometry to two equivalent Co(1), three equivalent Co(2), two equivalent Si(1), four equivalent Si(2), and four equivalent Si(3) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to four equivalent Tb(1), two equivalent Co(1), two equivalent Si(2), and four equivalent Si(3) atoms to form a mixture of distorted face and corner-sharing CoTb4Co2Si6 cuboctahedra. In the second Co site, Co(2) is bonded in a 8-coordinate geometry to three equivalent Tb(1), one Si(3), two equivalent Si(1), and two equivalent Si(2) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to four equivalent Tb(1) and four equivalent Co(2) atoms. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to four equivalent Tb(1), one Co(1), two equivalent Co(2), two equivalent Si(2), and two equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Tb(1), one Co(2), two equivalent Co(1), and two equivalent Si(2) atoms.
Tb2Co3Si5 crystallizes in the orthorhombic Ibam space group. Tb(1) is bonded in a 13-coordinate geometry to two equivalent Co(1), three equivalent Co(2), two equivalent Si(1), four equivalent Si(2), and four equivalent Si(3) atoms. Both Tb(1)-Co(1) bond lengths are 3.28 Å. There is one shorter (2.99 Å) and two longer (3.03 Å) Tb(1)-Co(2) bond lengths. Both Tb(1)-Si(1) bond lengths are 3.04 Å. There are two shorter (3.07 Å) and two longer (3.09 Å) Tb(1)-Si(2) bond lengths. There are a spread of Tb(1)-Si(3) bond distances ranging from 2.85-3.09 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to four equivalent Tb(1), two equivalent Co(1), two equivalent Si(2), and four equivalent Si(3) atoms to form a mixture of distorted face and corner-sharing CoTb4Co2Si6 cuboctahedra. Both Co(1)-Co(1) bond lengths are 2.78 Å. Both Co(1)-Si(2) bond lengths are 2.57 Å. All Co(1)-Si(3) bond lengths are 2.35 Å. In the second Co site, Co(2) is bonded in a 8-coordinate geometry to three equivalent Tb(1), one Si(3), two equivalent Si(1), and two equivalent Si(2) atoms. The Co(2)-Si(3) bond length is 2.29 Å. Both Co(2)-Si(1) bond lengths are 2.33 Å. Both Co(2)-Si(2) bond lengths are 2.31 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to four equivalent Tb(1) and four equivalent Co(2) atoms. In the second Si site, Si(2) is bonded in a 11-coordinate geometry to four equivalent Tb(1), one Co(1), two equivalent Co(2), two equivalent Si(2), and two equivalent Si(3) atoms. Both Si(2)-Si(2) bond lengths are 2.78 Å. Both Si(2)-Si(3) bond lengths are 2.50 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Tb(1), one Co(2), two equivalent Co(1), and two equivalent Si(2) atoms.