Ho8CoGa3 crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one Co(1) and four equivalent Ga(1) atoms to form distorted HoGa4Co trigonal pyramids that share corners with two equivalent Ho(4)Ga6 octahedra, corners with three equivalent Ho(2)Ga3Co tetrahedra, corners with six equivalent Ho(1)Ga4Co trigonal pyramids,  an edgeedge with one Ho(2)Ga3Co tetrahedra, edges with four equivalent Ho(1)Ga4Co trigonal pyramids, and faces with two equivalent Ho(4)Ga6 octahedra. The corner-sharing octahedral tilt angles range from 54-58°. In the second Ho site, Ho(2) is bonded to one Co(1) and three equivalent Ga(1) atoms to form distorted HoGa3Co tetrahedra that share corners with six equivalent Ho(4)Ga6 octahedra, corners with nine equivalent Ho(1)Ga4Co trigonal pyramids, and edges with three equivalent Ho(1)Ga4Co trigonal pyramids. The corner-sharing octahedral tilt angles range from 16-47°. In the third Ho site, Ho(3) is bonded in a 3-coordinate geometry to one Co(1) and four equivalent Ga(1) atoms. In the fourth Ho site, Ho(4) is bonded to six equivalent Ga(1) atoms to form distorted HoGa6 octahedra that share corners with six equivalent Ho(2)Ga3Co tetrahedra, corners with six equivalent Ho(1)Ga4Co trigonal pyramids, faces with two equivalent Ho(4)Ga6 octahedra, and faces with six equivalent Ho(1)Ga4Co trigonal pyramids. Co(1) is bonded in a 7-coordinate geometry to one Ho(2), three equivalent Ho(1), and three equivalent Ho(3) atoms. Ga(1) is bonded in a 11-coordinate geometry to one Ho(2), two equivalent Ho(4), four equivalent Ho(1), and four equivalent Ho(3) atoms.
Ho8CoGa3 crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one Co(1) and four equivalent Ga(1) atoms to form distorted HoGa4Co trigonal pyramids that share corners with two equivalent Ho(4)Ga6 octahedra, corners with three equivalent Ho(2)Ga3Co tetrahedra, corners with six equivalent Ho(1)Ga4Co trigonal pyramids,  an edgeedge with one Ho(2)Ga3Co tetrahedra, edges with four equivalent Ho(1)Ga4Co trigonal pyramids, and faces with two equivalent Ho(4)Ga6 octahedra. The corner-sharing octahedral tilt angles range from 54-58°. The Ho(1)-Co(1) bond length is 2.81 Å. There are a spread of Ho(1)-Ga(1) bond distances ranging from 2.93-3.74 Å. In the second Ho site, Ho(2) is bonded to one Co(1) and three equivalent Ga(1) atoms to form distorted HoGa3Co tetrahedra that share corners with six equivalent Ho(4)Ga6 octahedra, corners with nine equivalent Ho(1)Ga4Co trigonal pyramids, and edges with three equivalent Ho(1)Ga4Co trigonal pyramids. The corner-sharing octahedral tilt angles range from 16-47°. The Ho(2)-Co(1) bond length is 2.64 Å. All Ho(2)-Ga(1) bond lengths are 3.07 Å. In the third Ho site, Ho(3) is bonded in a 3-coordinate geometry to one Co(1) and four equivalent Ga(1) atoms. The Ho(3)-Co(1) bond length is 2.77 Å. There are two shorter (3.15 Å) and two longer (3.69 Å) Ho(3)-Ga(1) bond lengths. In the fourth Ho site, Ho(4) is bonded to six equivalent Ga(1) atoms to form distorted HoGa6 octahedra that share corners with six equivalent Ho(2)Ga3Co tetrahedra, corners with six equivalent Ho(1)Ga4Co trigonal pyramids, faces with two equivalent Ho(4)Ga6 octahedra, and faces with six equivalent Ho(1)Ga4Co trigonal pyramids. There are three shorter (3.25 Å) and three longer (3.36 Å) Ho(4)-Ga(1) bond lengths. Co(1) is bonded in a 7-coordinate geometry to one Ho(2), three equivalent Ho(1), and three equivalent Ho(3) atoms. Ga(1) is bonded in a 11-coordinate geometry to one Ho(2), two equivalent Ho(4), four equivalent Ho(1), and four equivalent Ho(3) atoms.