Er2Al3Si2 crystallizes in the monoclinic C2/m space group. Er(1) is bonded in a 11-coordinate geometry to two equivalent Al(2), four equivalent Al(1), and five equivalent Si(1) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted water-like geometry to four equivalent Er(1) and two equivalent Si(1) atoms. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to four equivalent Er(1) and two equivalent Si(1) atoms. Si(1) is bonded in a 9-coordinate geometry to five equivalent Er(1), one Al(2), two equivalent Al(1), and one Si(1) atom.
Er2Al3Si2 crystallizes in the monoclinic C2/m space group. Er(1) is bonded in a 11-coordinate geometry to two equivalent Al(2), four equivalent Al(1), and five equivalent Si(1) atoms. Both Er(1)-Al(2) bond lengths are 2.99 Å. There are a spread of Er(1)-Al(1) bond distances ranging from 3.15-3.20 Å. There are a spread of Er(1)-Si(1) bond distances ranging from 2.84-2.97 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted water-like geometry to four equivalent Er(1) and two equivalent Si(1) atoms. Both Al(1)-Si(1) bond lengths are 2.59 Å. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to four equivalent Er(1) and two equivalent Si(1) atoms. Both Al(2)-Si(1) bond lengths are 2.69 Å. Si(1) is bonded in a 9-coordinate geometry to five equivalent Er(1), one Al(2), two equivalent Al(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.36 Å.