Gd2CoSi2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a 10-coordinate geometry to four equivalent Co(1), two equivalent Si(2), and five equivalent Si(1) atoms. In the second Gd site, Gd(2) is bonded in a 6-coordinate geometry to two equivalent Co(1), one Si(1), and five equivalent Si(2) atoms. Co(1) is bonded in a 10-coordinate geometry to two equivalent Gd(2), four equivalent Gd(1), one Si(2), and three equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Gd(2), five equivalent Gd(1), three equivalent Co(1), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Gd(1), five equivalent Gd(2), one Co(1), and one Si(2) atom.
Gd2CoSi2 crystallizes in the monoclinic C2/m space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a 10-coordinate geometry to four equivalent Co(1), two equivalent Si(2), and five equivalent Si(1) atoms. There are a spread of Gd(1)-Co(1) bond distances ranging from 2.94-3.18 Å. Both Gd(1)-Si(2) bond lengths are 2.88 Å. There are a spread of Gd(1)-Si(1) bond distances ranging from 2.97-3.28 Å. In the second Gd site, Gd(2) is bonded in a 6-coordinate geometry to two equivalent Co(1), one Si(1), and five equivalent Si(2) atoms. Both Gd(2)-Co(1) bond lengths are 3.33 Å. The Gd(2)-Si(1) bond length is 2.89 Å. There are a spread of Gd(2)-Si(2) bond distances ranging from 2.96-3.20 Å. Co(1) is bonded in a 10-coordinate geometry to two equivalent Gd(2), four equivalent Gd(1), one Si(2), and three equivalent Si(1) atoms. The Co(1)-Si(2) bond length is 2.49 Å. There is one shorter (2.32 Å) and two longer (2.35 Å) Co(1)-Si(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to one Gd(2), five equivalent Gd(1), three equivalent Co(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.86 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Gd(1), five equivalent Gd(2), one Co(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.56 Å.