Er(Mg4Al3)4 crystallizes in the cubic I-43m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to one Mg(2), six equivalent Mg(1), and five equivalent Al(1) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to three equivalent Mg(1), one Er(1), and six equivalent Al(1) atoms. Er(1) is bonded in a 16-coordinate geometry to four equivalent Mg(2) and twelve equivalent Al(1) atoms. Al(1) is bonded in a 11-coordinate geometry to two equivalent Mg(2), five equivalent Mg(1), one Er(1), and three equivalent Al(1) atoms.
Er(Mg4Al3)4 crystallizes in the cubic I-43m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to one Mg(2), six equivalent Mg(1), and five equivalent Al(1) atoms. The Mg(1)-Mg(2) bond length is 3.03 Å. There are two shorter (3.11 Å) and four longer (3.16 Å) Mg(1)-Mg(1) bond lengths. There are a spread of Mg(1)-Al(1) bond distances ranging from 2.87-3.18 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to three equivalent Mg(1), one Er(1), and six equivalent Al(1) atoms. The Mg(2)-Er(1) bond length is 3.26 Å. All Mg(2)-Al(1) bond lengths are 3.16 Å. Er(1) is bonded in a 16-coordinate geometry to four equivalent Mg(2) and twelve equivalent Al(1) atoms. All Er(1)-Al(1) bond lengths are 3.22 Å. Al(1) is bonded in a 11-coordinate geometry to two equivalent Mg(2), five equivalent Mg(1), one Er(1), and three equivalent Al(1) atoms. There is one shorter (2.71 Å) and two longer (2.77 Å) Al(1)-Al(1) bond lengths.