HoNi4Al crystallizes in the hexagonal P-6m2 space group. Ho(1) is bonded in a 18-coordinate geometry to three equivalent Ni(1), twelve equivalent Ni(2), and three equivalent Al(1) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Ho(1), six equivalent Ni(2), and three equivalent Al(1) atoms to form NiHo3Al3Ni6 cuboctahedra that share corners with nine equivalent Al(1)Ho3Ni9 cuboctahedra, corners with twelve equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with six equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with two equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with three equivalent Al(1)Ho3Ni9 cuboctahedra, and faces with eighteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra. In the second Ni site, Ni(2) is bonded to four equivalent Ho(1), two equivalent Ni(1), four equivalent Ni(2), and two equivalent Al(1) atoms to form distorted NiHo4Al2Ni6 cuboctahedra that share corners with four equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, corners with four equivalent Al(1)Ho3Ni9 cuboctahedra, corners with sixteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with ten equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, faces with six equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with six equivalent Al(1)Ho3Ni9 cuboctahedra, and faces with ten equivalent Ni(2)Ho4Al2Ni6 cuboctahedra. Al(1) is bonded to three equivalent Ho(1), three equivalent Ni(1), and six equivalent Ni(2) atoms to form distorted AlHo3Ni9 cuboctahedra that share corners with nine equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, corners with twelve equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with six equivalent Al(1)Ho3Ni9 cuboctahedra, faces with two equivalent Al(1)Ho3Ni9 cuboctahedra, faces with three equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, and faces with eighteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra.
HoNi4Al crystallizes in the hexagonal P-6m2 space group. Ho(1) is bonded in a 18-coordinate geometry to three equivalent Ni(1), twelve equivalent Ni(2), and three equivalent Al(1) atoms. All Ho(1)-Ni(1) bond lengths are 2.90 Å. All Ho(1)-Ni(2) bond lengths are 3.16 Å. All Ho(1)-Al(1) bond lengths are 2.90 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Ho(1), six equivalent Ni(2), and three equivalent Al(1) atoms to form NiHo3Al3Ni6 cuboctahedra that share corners with nine equivalent Al(1)Ho3Ni9 cuboctahedra, corners with twelve equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with six equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with two equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with three equivalent Al(1)Ho3Ni9 cuboctahedra, and faces with eighteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra. All Ni(1)-Ni(2) bond lengths are 2.40 Å. All Ni(1)-Al(1) bond lengths are 2.90 Å. In the second Ni site, Ni(2) is bonded to four equivalent Ho(1), two equivalent Ni(1), four equivalent Ni(2), and two equivalent Al(1) atoms to form distorted NiHo4Al2Ni6 cuboctahedra that share corners with four equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, corners with four equivalent Al(1)Ho3Ni9 cuboctahedra, corners with sixteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with ten equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, faces with six equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, faces with six equivalent Al(1)Ho3Ni9 cuboctahedra, and faces with ten equivalent Ni(2)Ho4Al2Ni6 cuboctahedra. There are two shorter (2.48 Å) and two longer (2.54 Å) Ni(2)-Ni(2) bond lengths. Both Ni(2)-Al(1) bond lengths are 2.42 Å. Al(1) is bonded to three equivalent Ho(1), three equivalent Ni(1), and six equivalent Ni(2) atoms to form distorted AlHo3Ni9 cuboctahedra that share corners with nine equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, corners with twelve equivalent Ni(2)Ho4Al2Ni6 cuboctahedra, edges with six equivalent Al(1)Ho3Ni9 cuboctahedra, faces with two equivalent Al(1)Ho3Ni9 cuboctahedra, faces with three equivalent Ni(1)Ho3Al3Ni6 cuboctahedra, and faces with eighteen equivalent Ni(2)Ho4Al2Ni6 cuboctahedra.