ErFeGe2 crystallizes in the orthorhombic Cmcm space group. Er(1) is bonded in a 14-coordinate geometry to four equivalent Fe(1), four equivalent Ge(2), and six equivalent Ge(1) atoms. Fe(1) is bonded in a 5-coordinate geometry to four equivalent Er(1), one Ge(1), and four equivalent Ge(2) atoms. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to six equivalent Er(1), one Fe(1), and two equivalent Ge(1) atoms. In the second Ge site, Ge(2) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Fe(1) atoms.
ErFeGe2 crystallizes in the orthorhombic Cmcm space group. Er(1) is bonded in a 14-coordinate geometry to four equivalent Fe(1), four equivalent Ge(2), and six equivalent Ge(1) atoms. All Er(1)-Fe(1) bond lengths are 3.18 Å. There are two shorter (3.11 Å) and two longer (3.14 Å) Er(1)-Ge(2) bond lengths. There are four shorter (3.14 Å) and two longer (3.29 Å) Er(1)-Ge(1) bond lengths. Fe(1) is bonded in a 5-coordinate geometry to four equivalent Er(1), one Ge(1), and four equivalent Ge(2) atoms. The Fe(1)-Ge(1) bond length is 2.26 Å. There are two shorter (2.37 Å) and two longer (2.38 Å) Fe(1)-Ge(2) bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to six equivalent Er(1), one Fe(1), and two equivalent Ge(1) atoms. Both Ge(1)-Ge(1) bond lengths are 2.57 Å. In the second Ge site, Ge(2) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Fe(1) atoms.