Sm2Co16Ge crystallizes in the trigonal R3m space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 19-coordinate geometry to one Co(5), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(3) atoms. In the second Sm site, Sm(2) is bonded in a 19-coordinate geometry to three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), six equivalent Co(2), and one Ge(1) atom. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to one Sm(1), one Sm(2), one Co(5), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Co(4), and one Ge(1) atom to form distorted CoSm2Co9Ge cuboctahedra that share corners with four equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with four equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with four equivalent Co(3)Sm3Co9 cuboctahedra, corners with twelve equivalent Co(1)Sm2Co9Ge cuboctahedra,  an edgeedge with one Co(1)Sm2Co9Ge cuboctahedra,  an edgeedge with one Co(2)Sm3Co8Ge cuboctahedra,  an edgeedge with one Co(3)Sm3Co9 cuboctahedra, edges with two equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with four equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with five equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with five equivalent Co(3)Sm3Co9 cuboctahedra, and faces with seven equivalent Co(1)Sm2Co9Ge cuboctahedra. In the second Co site, Co(2) is bonded to one Sm(1), two equivalent Sm(2), two equivalent Co(3), two equivalent Co(4), four equivalent Co(1), and one Ge(1) atom to form CoSm3Co8Ge cuboctahedra that share corners with two equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with five equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(3)Sm3Co9 cuboctahedra,  an edgeedge with one Co(3)Sm3Co9 cuboctahedra, edges with two equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(4)Sm2Co9Ge cuboctahedra, edges with four equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with three equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(3)Sm3Co9 cuboctahedra, faces with four equivalent Co(2)Sm3Co8Ge cuboctahedra, and faces with ten equivalent Co(1)Sm2Co9Ge cuboctahedra. In the third Co site, Co(3) is bonded to one Sm(2), two equivalent Sm(1), one Co(5), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(1) atoms to form CoSm3Co9 cuboctahedra that share corners with two equivalent Co(3)Sm3Co9 cuboctahedra, corners with five equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(2)Sm3Co8Ge cuboctahedra,  an edgeedge with one Co(2)Sm3Co8Ge cuboctahedra, edges with two equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(4)Sm2Co9Ge cuboctahedra, edges with four equivalent Co(3)Sm3Co9 cuboctahedra, faces with three equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with four equivalent Co(3)Sm3Co9 cuboctahedra, and faces with ten equivalent Co(1)Sm2Co9Ge cuboctahedra. In the fourth Co site, Co(4) is bonded to one Sm(1), one Sm(2), one Co(5), two equivalent Co(2), two equivalent Co(3), four equivalent Co(1), and one Ge(1) atom to form distorted CoSm2Co9Ge cuboctahedra that share corners with four equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with five equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with five equivalent Co(3)Sm3Co9 cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(2)Sm3Co8Ge cuboctahedra, edges with three equivalent Co(3)Sm3Co9 cuboctahedra, edges with four equivalent Co(1)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with three equivalent Co(3)Sm3Co9 cuboctahedra, faces with four equivalent Co(4)Sm2Co9Ge cuboctahedra, and faces with eight equivalent Co(1)Sm2Co9Ge cuboctahedra. In the fifth Co site, Co(5) is bonded in a 14-coordinate geometry to one Sm(1), three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), and one Ge(1) atom. Ge(1) is bonded in a 14-coordinate geometry to one Sm(2), one Co(5), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(1) atoms.
Sm2Co16Ge crystallizes in the trigonal R3m space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 19-coordinate geometry to one Co(5), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(3) atoms. The Sm(1)-Co(5) bond length is 2.98 Å. All Sm(1)-Co(2) bond lengths are 2.96 Å. All Sm(1)-Co(4) bond lengths are 3.21 Å. All Sm(1)-Co(1) bond lengths are 3.00 Å. There are three shorter (3.12 Å) and three longer (3.19 Å) Sm(1)-Co(3) bond lengths. In the second Sm site, Sm(2) is bonded in a 19-coordinate geometry to three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), six equivalent Co(2), and one Ge(1) atom. All Sm(2)-Co(3) bond lengths are 2.97 Å. All Sm(2)-Co(4) bond lengths are 3.31 Å. All Sm(2)-Co(1) bond lengths are 3.01 Å. There are three shorter (3.14 Å) and three longer (3.17 Å) Sm(2)-Co(2) bond lengths. The Sm(2)-Ge(1) bond length is 3.06 Å. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to one Sm(1), one Sm(2), one Co(5), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Co(4), and one Ge(1) atom to form distorted CoSm2Co9Ge cuboctahedra that share corners with four equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with four equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with four equivalent Co(3)Sm3Co9 cuboctahedra, corners with twelve equivalent Co(1)Sm2Co9Ge cuboctahedra,  an edgeedge with one Co(1)Sm2Co9Ge cuboctahedra,  an edgeedge with one Co(2)Sm3Co8Ge cuboctahedra,  an edgeedge with one Co(3)Sm3Co9 cuboctahedra, edges with two equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with four equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with five equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with five equivalent Co(3)Sm3Co9 cuboctahedra, and faces with seven equivalent Co(1)Sm2Co9Ge cuboctahedra. The Co(1)-Co(5) bond length is 2.70 Å. Both Co(1)-Co(1) bond lengths are 2.42 Å. There is one shorter (2.53 Å) and one longer (2.58 Å) Co(1)-Co(2) bond length. There is one shorter (2.50 Å) and one longer (2.59 Å) Co(1)-Co(3) bond length. There is one shorter (2.38 Å) and one longer (2.39 Å) Co(1)-Co(4) bond length. The Co(1)-Ge(1) bond length is 2.70 Å. In the second Co site, Co(2) is bonded to one Sm(1), two equivalent Sm(2), two equivalent Co(3), two equivalent Co(4), four equivalent Co(1), and one Ge(1) atom to form CoSm3Co8Ge cuboctahedra that share corners with two equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with five equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(3)Sm3Co9 cuboctahedra,  an edgeedge with one Co(3)Sm3Co9 cuboctahedra, edges with two equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(4)Sm2Co9Ge cuboctahedra, edges with four equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with three equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(3)Sm3Co9 cuboctahedra, faces with four equivalent Co(2)Sm3Co8Ge cuboctahedra, and faces with ten equivalent Co(1)Sm2Co9Ge cuboctahedra. Both Co(2)-Co(3) bond lengths are 2.46 Å. Both Co(2)-Co(4) bond lengths are 2.44 Å. The Co(2)-Ge(1) bond length is 2.63 Å. In the third Co site, Co(3) is bonded to one Sm(2), two equivalent Sm(1), one Co(5), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(1) atoms to form CoSm3Co9 cuboctahedra that share corners with two equivalent Co(3)Sm3Co9 cuboctahedra, corners with five equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, corners with eight equivalent Co(2)Sm3Co8Ge cuboctahedra,  an edgeedge with one Co(2)Sm3Co8Ge cuboctahedra, edges with two equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(4)Sm2Co9Ge cuboctahedra, edges with four equivalent Co(3)Sm3Co9 cuboctahedra, faces with three equivalent Co(4)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with four equivalent Co(3)Sm3Co9 cuboctahedra, and faces with ten equivalent Co(1)Sm2Co9Ge cuboctahedra. The Co(3)-Co(5) bond length is 2.59 Å. Both Co(3)-Co(4) bond lengths are 2.40 Å. In the fourth Co site, Co(4) is bonded to one Sm(1), one Sm(2), one Co(5), two equivalent Co(2), two equivalent Co(3), four equivalent Co(1), and one Ge(1) atom to form distorted CoSm2Co9Ge cuboctahedra that share corners with four equivalent Co(4)Sm2Co9Ge cuboctahedra, corners with five equivalent Co(2)Sm3Co8Ge cuboctahedra, corners with five equivalent Co(3)Sm3Co9 cuboctahedra, corners with eight equivalent Co(1)Sm2Co9Ge cuboctahedra, edges with three equivalent Co(2)Sm3Co8Ge cuboctahedra, edges with three equivalent Co(3)Sm3Co9 cuboctahedra, edges with four equivalent Co(1)Sm2Co9Ge cuboctahedra, faces with three equivalent Co(2)Sm3Co8Ge cuboctahedra, faces with three equivalent Co(3)Sm3Co9 cuboctahedra, faces with four equivalent Co(4)Sm2Co9Ge cuboctahedra, and faces with eight equivalent Co(1)Sm2Co9Ge cuboctahedra. The Co(4)-Co(5) bond length is 2.53 Å. The Co(4)-Ge(1) bond length is 2.59 Å. In the fifth Co site, Co(5) is bonded in a 14-coordinate geometry to one Sm(1), three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), and one Ge(1) atom. The Co(5)-Ge(1) bond length is 2.40 Å. Ge(1) is bonded in a 14-coordinate geometry to one Sm(2), one Co(5), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(1) atoms.