ErNi5 crystallizes in the hexagonal P6/mmm space group. Er(1) is bonded in a distorted hexagonal planar geometry to six equivalent Ni(2) and twelve equivalent Ni(1) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Er(1), four equivalent Ni(1), and four equivalent Ni(2) atoms to form a mixture of edge, corner, and face-sharing NiEr4Ni8 cuboctahedra. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Er(1) and six equivalent Ni(1) atoms.
ErNi5 crystallizes in the hexagonal P6/mmm space group. Er(1) is bonded in a distorted hexagonal planar geometry to six equivalent Ni(2) and twelve equivalent Ni(1) atoms. All Er(1)-Ni(2) bond lengths are 2.77 Å. All Er(1)-Ni(1) bond lengths are 3.10 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Er(1), four equivalent Ni(1), and four equivalent Ni(2) atoms to form a mixture of edge, corner, and face-sharing NiEr4Ni8 cuboctahedra. All Ni(1)-Ni(1) bond lengths are 2.40 Å. All Ni(1)-Ni(2) bond lengths are 2.40 Å. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Er(1) and six equivalent Ni(1) atoms.