Er3Fe2Si3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 9-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), and three equivalent Si(1) atoms. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to four equivalent Fe(1), two equivalent Si(1), and five equivalent Si(2) atoms. Fe(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), one Si(1), and three equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Er(1), four equivalent Er(2), and two equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Er(1), five equivalent Er(2), three equivalent Fe(1), and one Si(2) atom.
Er3Fe2Si3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 9-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), and three equivalent Si(1) atoms. All Er(1)-Fe(1) bond lengths are 3.18 Å. Both Er(1)-Si(2) bond lengths are 2.88 Å. There are two shorter (2.88 Å) and one longer (3.17 Å) Er(1)-Si(1) bond length. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to four equivalent Fe(1), two equivalent Si(1), and five equivalent Si(2) atoms. There are a spread of Er(2)-Fe(1) bond distances ranging from 2.98-3.09 Å. Both Er(2)-Si(1) bond lengths are 2.93 Å. There are a spread of Er(2)-Si(2) bond distances ranging from 2.94-3.28 Å. Fe(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), one Si(1), and three equivalent Si(2) atoms. The Fe(1)-Si(1) bond length is 2.58 Å. There are two shorter (2.36 Å) and one longer (2.40 Å) Fe(1)-Si(2) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Er(1), four equivalent Er(2), and two equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Er(1), five equivalent Er(2), three equivalent Fe(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.66 Å.