ErCBi2 crystallizes in the tetragonal P4_2/mbc space group. Er(1) is bonded in a 2-coordinate geometry to two equivalent C(1), two equivalent Bi(2), and four equivalent Bi(1) atoms. C(1) is bonded in a 6-coordinate geometry to two equivalent Er(1) and four equivalent Bi(2) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to four equivalent Er(1) and two equivalent Bi(1) atoms. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to two equivalent Er(1) and four equivalent C(1) atoms.
ErCBi2 crystallizes in the tetragonal P4_2/mbc space group. Er(1) is bonded in a 2-coordinate geometry to two equivalent C(1), two equivalent Bi(2), and four equivalent Bi(1) atoms. Both Er(1)-C(1) bond lengths are 2.79 Å. Both Er(1)-Bi(2) bond lengths are 3.05 Å. All Er(1)-Bi(1) bond lengths are 3.50 Å. C(1) is bonded in a 6-coordinate geometry to two equivalent Er(1) and four equivalent Bi(2) atoms. There are two shorter (2.47 Å) and two longer (2.83 Å) C(1)-Bi(2) bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to four equivalent Er(1) and two equivalent Bi(1) atoms. Both Bi(1)-Bi(1) bond lengths are 2.81 Å. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to two equivalent Er(1) and four equivalent C(1) atoms.