SmNi3 crystallizes in the monoclinic C2/m 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 Ni(2), three equivalent Ni(4), and six equivalent Ni(1) atoms. In the second Sm site, Sm(2) is bonded in a 6-coordinate geometry to four equivalent Ni(2), six equivalent Ni(3), and eight equivalent Ni(1) atoms. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Ni(4), two equivalent Ni(1), two equivalent Ni(2), and two equivalent Ni(3) atoms to form NiSm5Ni7 cuboctahedra that share corners with two equivalent Ni(4)Sm6Ni6 cuboctahedra, corners with four equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eleven equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with two equivalent Ni(2)Sm5Ni7 cuboctahedra, edges with six equivalent Ni(1)Sm5Ni7 cuboctahedra, faces with three equivalent Ni(4)Sm6Ni6 cuboctahedra, faces with five equivalent Ni(2)Sm5Ni7 cuboctahedra, and faces with six equivalent Ni(1)Sm5Ni7 cuboctahedra. In the second Ni site, Ni(2) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Ni(4), two equivalent Ni(3), and four equivalent Ni(1) atoms to form NiSm5Ni7 cuboctahedra that share corners with two equivalent Ni(4)Sm6Ni6 cuboctahedra, corners with seven equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eight equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with four equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with four equivalent Ni(2)Sm5Ni7 cuboctahedra,  a faceface with one Ni(2)Sm5Ni7 cuboctahedra, faces with three equivalent Ni(4)Sm6Ni6 cuboctahedra, and faces with ten equivalent Ni(1)Sm5Ni7 cuboctahedra. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Sm(2), two equivalent Ni(2), and four equivalent Ni(1) atoms. In the fourth Ni site, Ni(4) is bonded to six equivalent Sm(1), two equivalent Ni(2), and four equivalent Ni(1) atoms to form NiSm6Ni6 cuboctahedra that share corners with four equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eight equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with six equivalent Ni(4)Sm6Ni6 cuboctahedra, faces with six equivalent Ni(2)Sm5Ni7 cuboctahedra, and faces with twelve equivalent Ni(1)Sm5Ni7 cuboctahedra.
SmNi3 crystallizes in the monoclinic C2/m 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 Ni(2), three equivalent Ni(4), and six equivalent Ni(1) atoms. There are two shorter (2.86 Å) and one longer (3.12 Å) Sm(1)-Ni(2) bond length. There is one shorter (2.94 Å) and two longer (2.95 Å) Sm(1)-Ni(4) bond lengths. There are a spread of Sm(1)-Ni(1) bond distances ranging from 2.85-3.12 Å. In the second Sm site, Sm(2) is bonded in a 6-coordinate geometry to four equivalent Ni(2), six equivalent Ni(3), and eight equivalent Ni(1) atoms. All Sm(2)-Ni(2) bond lengths are 3.17 Å. All Sm(2)-Ni(3) bond lengths are 2.87 Å. There are four shorter (3.16 Å) and four longer (3.17 Å) Sm(2)-Ni(1) bond lengths. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Ni(4), two equivalent Ni(1), two equivalent Ni(2), and two equivalent Ni(3) atoms to form NiSm5Ni7 cuboctahedra that share corners with two equivalent Ni(4)Sm6Ni6 cuboctahedra, corners with four equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eleven equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with two equivalent Ni(2)Sm5Ni7 cuboctahedra, edges with six equivalent Ni(1)Sm5Ni7 cuboctahedra, faces with three equivalent Ni(4)Sm6Ni6 cuboctahedra, faces with five equivalent Ni(2)Sm5Ni7 cuboctahedra, and faces with six equivalent Ni(1)Sm5Ni7 cuboctahedra. The Ni(1)-Ni(4) bond length is 2.53 Å. There is one shorter (2.48 Å) and one longer (2.49 Å) Ni(1)-Ni(1) bond length. Both Ni(1)-Ni(2) bond lengths are 2.48 Å. There is one shorter (2.43 Å) and one longer (2.44 Å) Ni(1)-Ni(3) bond length. In the second Ni site, Ni(2) is bonded to two equivalent Sm(2), three equivalent Sm(1), one Ni(4), two equivalent Ni(3), and four equivalent Ni(1) atoms to form NiSm5Ni7 cuboctahedra that share corners with two equivalent Ni(4)Sm6Ni6 cuboctahedra, corners with seven equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eight equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with four equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with four equivalent Ni(2)Sm5Ni7 cuboctahedra,  a faceface with one Ni(2)Sm5Ni7 cuboctahedra, faces with three equivalent Ni(4)Sm6Ni6 cuboctahedra, and faces with ten equivalent Ni(1)Sm5Ni7 cuboctahedra. The Ni(2)-Ni(4) bond length is 2.54 Å. There is one shorter (2.42 Å) and one longer (2.44 Å) Ni(2)-Ni(3) bond length. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Sm(2), two equivalent Ni(2), and four equivalent Ni(1) atoms. In the fourth Ni site, Ni(4) is bonded to six equivalent Sm(1), two equivalent Ni(2), and four equivalent Ni(1) atoms to form NiSm6Ni6 cuboctahedra that share corners with four equivalent Ni(2)Sm5Ni7 cuboctahedra, corners with eight equivalent Ni(1)Sm5Ni7 cuboctahedra, edges with six equivalent Ni(4)Sm6Ni6 cuboctahedra, faces with six equivalent Ni(2)Sm5Ni7 cuboctahedra, and faces with twelve equivalent Ni(1)Sm5Ni7 cuboctahedra.