Sm2Co17 crystallizes in the trigonal R-3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Co(1), three equivalent Co(2), six equivalent Co(3), and nine equivalent Co(4) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Sm(1), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. In the second Co site, Co(2) is bonded to two equivalent Sm(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoSm2Co10 cuboctahedra that share corners with four equivalent Co(2)Sm2Co10 cuboctahedra, corners with ten equivalent Co(4)Sm3Co9 cuboctahedra, edges with six equivalent Co(4)Sm3Co9 cuboctahedra, faces with four equivalent Co(2)Sm2Co10 cuboctahedra, and faces with six equivalent Co(4)Sm3Co9 cuboctahedra. In the third Co site, Co(3) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms. In the fourth Co site, Co(4) is bonded to three equivalent Sm(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form CoSm3Co9 cuboctahedra that share corners with five equivalent Co(2)Sm2Co10 cuboctahedra, corners with ten equivalent Co(4)Sm3Co9 cuboctahedra, edges with three equivalent Co(2)Sm2Co10 cuboctahedra, edges with five equivalent Co(4)Sm3Co9 cuboctahedra, faces with three equivalent Co(2)Sm2Co10 cuboctahedra, and faces with seven equivalent Co(4)Sm3Co9 cuboctahedra.
Sm2Co17 crystallizes in the trigonal R-3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Co(1), three equivalent Co(2), six equivalent Co(3), and nine equivalent Co(4) atoms. The Sm(1)-Co(1) bond length is 3.03 Å. All Sm(1)-Co(2) bond lengths are 3.24 Å. All Sm(1)-Co(3) bond lengths are 3.01 Å. There are a spread of Sm(1)-Co(4) bond distances ranging from 3.01-3.20 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Sm(1), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. The Co(1)-Co(1) bond length is 2.35 Å. All Co(1)-Co(2) bond lengths are 2.56 Å. All Co(1)-Co(4) bond lengths are 2.59 Å. All Co(1)-Co(3) bond lengths are 2.67 Å. In the second Co site, Co(2) is bonded to two equivalent Sm(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoSm2Co10 cuboctahedra that share corners with four equivalent Co(2)Sm2Co10 cuboctahedra, corners with ten equivalent Co(4)Sm3Co9 cuboctahedra, edges with six equivalent Co(4)Sm3Co9 cuboctahedra, faces with four equivalent Co(2)Sm2Co10 cuboctahedra, and faces with six equivalent Co(4)Sm3Co9 cuboctahedra. All Co(2)-Co(3) bond lengths are 2.39 Å. All Co(2)-Co(4) bond lengths are 2.41 Å. In the third Co site, Co(3) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms. Both Co(3)-Co(3) bond lengths are 2.40 Å. There are two shorter (2.52 Å) and two longer (2.59 Å) Co(3)-Co(4) bond lengths. In the fourth Co site, Co(4) is bonded to three equivalent Sm(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form CoSm3Co9 cuboctahedra that share corners with five equivalent Co(2)Sm2Co10 cuboctahedra, corners with ten equivalent Co(4)Sm3Co9 cuboctahedra, edges with three equivalent Co(2)Sm2Co10 cuboctahedra, edges with five equivalent Co(4)Sm3Co9 cuboctahedra, faces with three equivalent Co(2)Sm2Co10 cuboctahedra, and faces with seven equivalent Co(4)Sm3Co9 cuboctahedra. Both Co(4)-Co(4) bond lengths are 2.47 Å.