Er5Si3C crystallizes in the hexagonal P6_3/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to six equivalent Si(1) atoms. In the second Er site, Er(2) is bonded in a 2-coordinate geometry to five equivalent Si(1) and two equivalent C(1) atoms. Si(1) is bonded in a 9-coordinate geometry to four equivalent Er(1) and five equivalent Er(2) atoms. C(1) is bonded to six equivalent Er(2) atoms to form face-sharing CEr6 octahedra.
Er5Si3C crystallizes in the hexagonal P6_3/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to six equivalent Si(1) atoms. All Er(1)-Si(1) bond lengths are 2.99 Å. In the second Er site, Er(2) is bonded in a 2-coordinate geometry to five equivalent Si(1) and two equivalent C(1) atoms. There are a spread of Er(2)-Si(1) bond distances ranging from 2.96-3.49 Å. Both Er(2)-C(1) bond lengths are 2.45 Å. Si(1) is bonded in a 9-coordinate geometry to four equivalent Er(1) and five equivalent Er(2) atoms. C(1) is bonded to six equivalent Er(2) atoms to form face-sharing CEr6 octahedra.