Sm2Co7 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. In the second Sm site, Sm(2) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to six equivalent Sm(1) and six equivalent Co(5) atoms to form CoSm6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Sm5Co7 cuboctahedra, edges with six equivalent Co(1)Sm6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Sm5Co7 cuboctahedra. In the second Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Sm(2), three equivalent Co(4), and three equivalent Co(5) atoms. In the third Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Sm(2), three equivalent Co(4), and three equivalent Co(5) atoms. In the fourth Co site, Co(4) is bonded to four equivalent Sm(2), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoSm4Co8 cuboctahedra that share corners with four equivalent Co(4)Sm4Co8 cuboctahedra, corners with twelve equivalent Co(5)Sm5Co7 cuboctahedra, edges with two equivalent Co(4)Sm4Co8 cuboctahedra, edges with eight equivalent Co(5)Sm5Co7 cuboctahedra, faces with two equivalent Co(5)Sm5Co7 cuboctahedra, and faces with eight equivalent Co(4)Sm4Co8 cuboctahedra. In the fifth Co site, Co(5) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoSm5Co7 cuboctahedra that share corners with two equivalent Co(1)Sm6Co6 cuboctahedra, corners with six equivalent Co(4)Sm4Co8 cuboctahedra, corners with nine equivalent Co(5)Sm5Co7 cuboctahedra, edges with four equivalent Co(4)Sm4Co8 cuboctahedra, edges with four equivalent Co(5)Sm5Co7 cuboctahedra,  a faceface with one Co(4)Sm4Co8 cuboctahedra, faces with three equivalent Co(1)Sm6Co6 cuboctahedra, and faces with ten equivalent Co(5)Sm5Co7 cuboctahedra.
Sm2Co7 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. All Sm(1)-Co(1) bond lengths are 2.97 Å. There are six shorter (2.90 Å) and three longer (3.16 Å) Sm(1)-Co(5) bond lengths. In the second Sm site, Sm(2) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. All Sm(2)-Co(2) bond lengths are 2.90 Å. All Sm(2)-Co(3) bond lengths are 2.90 Å. All Sm(2)-Co(4) bond lengths are 3.13 Å. All Sm(2)-Co(5) bond lengths are 3.25 Å. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to six equivalent Sm(1) and six equivalent Co(5) atoms to form CoSm6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Sm5Co7 cuboctahedra, edges with six equivalent Co(1)Sm6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Sm5Co7 cuboctahedra. All Co(1)-Co(5) bond lengths are 2.57 Å. In the second Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Sm(2), three equivalent Co(4), and three equivalent Co(5) atoms. All Co(2)-Co(4) bond lengths are 2.46 Å. All Co(2)-Co(5) bond lengths are 2.43 Å. In the third Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Sm(2), three equivalent Co(4), and three equivalent Co(5) atoms. All Co(3)-Co(4) bond lengths are 2.46 Å. All Co(3)-Co(5) bond lengths are 2.44 Å. In the fourth Co site, Co(4) is bonded to four equivalent Sm(2), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoSm4Co8 cuboctahedra that share corners with four equivalent Co(4)Sm4Co8 cuboctahedra, corners with twelve equivalent Co(5)Sm5Co7 cuboctahedra, edges with two equivalent Co(4)Sm4Co8 cuboctahedra, edges with eight equivalent Co(5)Sm5Co7 cuboctahedra, faces with two equivalent Co(5)Sm5Co7 cuboctahedra, and faces with eight equivalent Co(4)Sm4Co8 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co(4)-Co(4) bond lengths. In the fifth Co site, Co(5) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoSm5Co7 cuboctahedra that share corners with two equivalent Co(1)Sm6Co6 cuboctahedra, corners with six equivalent Co(4)Sm4Co8 cuboctahedra, corners with nine equivalent Co(5)Sm5Co7 cuboctahedra, edges with four equivalent Co(4)Sm4Co8 cuboctahedra, edges with four equivalent Co(5)Sm5Co7 cuboctahedra,  a faceface with one Co(4)Sm4Co8 cuboctahedra, faces with three equivalent Co(1)Sm6Co6 cuboctahedra, and faces with ten equivalent Co(5)Sm5Co7 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co(5)-Co(5) bond lengths.