ErMn4Al8 crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded in a 20-coordinate geometry to eight equivalent Mn(1), four equivalent Al(1), and eight equivalent Al(2) atoms. Mn(1) is bonded to two equivalent Er(1), two equivalent Mn(1), four equivalent Al(1), and four equivalent Al(2) atoms to form a mixture of distorted face, corner, and edge-sharing MnEr2Mn2Al8 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 10-coordinate geometry to one Er(1), four equivalent Mn(1), one Al(1), and four equivalent Al(2) atoms. In the second Al site, Al(2) is bonded in a 12-coordinate geometry to two equivalent Er(1), four equivalent Mn(1), two equivalent Al(2), and four equivalent Al(1) atoms.
ErMn4Al8 crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded in a 20-coordinate geometry to eight equivalent Mn(1), four equivalent Al(1), and eight equivalent Al(2) atoms. All Er(1)-Mn(1) bond lengths are 3.35 Å. All Er(1)-Al(1) bond lengths are 2.93 Å. All Er(1)-Al(2) bond lengths are 3.23 Å. Mn(1) is bonded to two equivalent Er(1), two equivalent Mn(1), four equivalent Al(1), and four equivalent Al(2) atoms to form a mixture of distorted face, corner, and edge-sharing MnEr2Mn2Al8 cuboctahedra. Both Mn(1)-Mn(1) bond lengths are 2.57 Å. All Mn(1)-Al(1) bond lengths are 2.64 Å. All Mn(1)-Al(2) bond lengths are 2.54 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 10-coordinate geometry to one Er(1), four equivalent Mn(1), one Al(1), and four equivalent Al(2) atoms. The Al(1)-Al(1) bond length is 2.87 Å. There are two shorter (2.75 Å) and two longer (2.81 Å) Al(1)-Al(2) bond lengths. In the second Al site, Al(2) is bonded in a 12-coordinate geometry to two equivalent Er(1), four equivalent Mn(1), two equivalent Al(2), and four equivalent Al(1) atoms. Both Al(2)-Al(2) bond lengths are 2.77 Å.