SmCo9Si2 crystallizes in the tetragonal I4_1/amd space group. Sm(1) is bonded in a 18-coordinate geometry to two equivalent Co(1) and sixteen equivalent Co(2) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to two equivalent Sm(1), eight equivalent Co(2), and four equivalent Si(1) atoms. In the second Co site, Co(2) is bonded to two equivalent Sm(1), one Co(1), seven equivalent Co(2), and two equivalent Si(1) atoms to form a mixture of distorted edge, face, and corner-sharing CoSm2Co8Si2 cuboctahedra. Si(1) is bonded in a 10-coordinate geometry to two equivalent Co(1) and eight equivalent Co(2) atoms.
SmCo9Si2 crystallizes in the tetragonal I4_1/amd space group. Sm(1) is bonded in a 18-coordinate geometry to two equivalent Co(1) and sixteen equivalent Co(2) atoms. Both Sm(1)-Co(1) bond lengths are 3.15 Å. There are eight shorter (3.04 Å) and eight longer (3.12 Å) Sm(1)-Co(2) bond lengths. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to two equivalent Sm(1), eight equivalent Co(2), and four equivalent Si(1) atoms. All Co(1)-Co(2) bond lengths are 2.62 Å. All Co(1)-Si(1) bond lengths are 2.55 Å. In the second Co site, Co(2) is bonded to two equivalent Sm(1), one Co(1), seven equivalent Co(2), and two equivalent Si(1) atoms to form a mixture of distorted edge, face, and corner-sharing CoSm2Co8Si2 cuboctahedra. There are a spread of Co(2)-Co(2) bond distances ranging from 2.40-2.64 Å. There is one shorter (2.36 Å) and one longer (2.38 Å) Co(2)-Si(1) bond length. Si(1) is bonded in a 10-coordinate geometry to two equivalent Co(1) and eight equivalent Co(2) atoms.