Ho2Co12Ni5 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 18-coordinate geometry to six equivalent Co(1) and twelve equivalent Co(2) atoms. In the second Ho site, Ho(2) is bonded in a 20-coordinate geometry to six equivalent Co(1), six equivalent Co(2), two equivalent Ni(1), and six equivalent Ni(2) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Ho(1), one Ho(2), two equivalent Co(1), four equivalent Co(2), two equivalent Ni(1), and two equivalent Ni(2) atoms to form distorted CoHo2Co6Ni4 cuboctahedra that share corners with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(2)Ho3Co6Ni3 cuboctahedra, corners with twelve equivalent Co(1)Ho2Co6Ni4 cuboctahedra,  an edgeedge with one Co(1)Ho2Co6Ni4 cuboctahedra, edges with two equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with two equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with seven equivalent Co(1)Ho2Co6Ni4 cuboctahedra, and faces with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra. In the second Co site, Co(2) is bonded to one Ho(2), two equivalent Ho(1), two equivalent Co(2), four equivalent Co(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted CoHo3Co6Ni3 cuboctahedra that share corners with five equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra, corners with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with two equivalent Co(1)Ho2Co6Ni4 cuboctahedra, edges with three equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, edges with five equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with two equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with eight equivalent Co(2)Ho3Co6Ni3 cuboctahedra, and faces with ten equivalent Co(1)Ho2Co6Ni4 cuboctahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(2) is bonded to two equivalent Ho(2), four equivalent Co(1), four equivalent Co(2), and two equivalent Ni(1) atoms to form NiHo2Co8Ni2 cuboctahedra that share corners with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra, corners with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with four equivalent Co(1)Ho2Co6Ni4 cuboctahedra, edges with six equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with four equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with six equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, and faces with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra. In the second Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Ho(2), three equivalent Co(2), six equivalent Co(1), one Ni(1), and three equivalent Ni(2) atoms.
Ho2Co12Ni5 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 18-coordinate geometry to six equivalent Co(1) and twelve equivalent Co(2) atoms. All Ho(1)-Co(1) bond lengths are 2.94 Å. There are six shorter (2.95 Å) and six longer (3.20 Å) Ho(1)-Co(2) bond lengths. In the second Ho site, Ho(2) is bonded in a 20-coordinate geometry to six equivalent Co(1), six equivalent Co(2), two equivalent Ni(1), and six equivalent Ni(2) atoms. All Ho(2)-Co(1) bond lengths are 3.01 Å. All Ho(2)-Co(2) bond lengths are 3.05 Å. Both Ho(2)-Ni(1) bond lengths are 2.80 Å. All Ho(2)-Ni(2) bond lengths are 3.12 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Ho(1), one Ho(2), two equivalent Co(1), four equivalent Co(2), two equivalent Ni(1), and two equivalent Ni(2) atoms to form distorted CoHo2Co6Ni4 cuboctahedra that share corners with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(2)Ho3Co6Ni3 cuboctahedra, corners with twelve equivalent Co(1)Ho2Co6Ni4 cuboctahedra,  an edgeedge with one Co(1)Ho2Co6Ni4 cuboctahedra, edges with two equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with two equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with seven equivalent Co(1)Ho2Co6Ni4 cuboctahedra, and faces with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra. There is one shorter (2.30 Å) and one longer (2.46 Å) Co(1)-Co(1) bond length. There are two shorter (2.51 Å) and two longer (2.53 Å) Co(1)-Co(2) bond lengths. Both Co(1)-Ni(1) bond lengths are 2.67 Å. Both Co(1)-Ni(2) bond lengths are 2.38 Å. In the second Co site, Co(2) is bonded to one Ho(2), two equivalent Ho(1), two equivalent Co(2), four equivalent Co(1), one Ni(1), and two equivalent Ni(2) atoms to form distorted CoHo3Co6Ni3 cuboctahedra that share corners with five equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra, corners with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with two equivalent Co(1)Ho2Co6Ni4 cuboctahedra, edges with three equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, edges with five equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with two equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, faces with eight equivalent Co(2)Ho3Co6Ni3 cuboctahedra, and faces with ten equivalent Co(1)Ho2Co6Ni4 cuboctahedra. Both Co(2)-Co(2) bond lengths are 2.36 Å. The Co(2)-Ni(1) bond length is 2.65 Å. Both Co(2)-Ni(2) bond lengths are 2.43 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(2) is bonded to two equivalent Ho(2), four equivalent Co(1), four equivalent Co(2), and two equivalent Ni(1) atoms to form NiHo2Co8Ni2 cuboctahedra that share corners with four equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, corners with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra, corners with ten equivalent Co(2)Ho3Co6Ni3 cuboctahedra, edges with four equivalent Co(1)Ho2Co6Ni4 cuboctahedra, edges with six equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with four equivalent Co(2)Ho3Co6Ni3 cuboctahedra, faces with six equivalent Ni(2)Ho2Co8Ni2 cuboctahedra, and faces with eight equivalent Co(1)Ho2Co6Ni4 cuboctahedra. Both Ni(2)-Ni(1) bond lengths are 2.52 Å. In the second Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Ho(2), three equivalent Co(2), six equivalent Co(1), one Ni(1), and three equivalent Ni(2) atoms. The Ni(1)-Ni(1) bond length is 2.42 Å.