Er3FeGe3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Ge(2) and four equivalent Ge(1) atoms. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to three equivalent Ge(2) and four equivalent Ge(1) atoms. Fe(1) is bonded to four equivalent Ge(1) atoms to form distorted edge-sharing FeGe4 cuboctahedra. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), and one Ge(2) atom. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to three equivalent Er(2), four equivalent Er(1), and two equivalent Ge(1) atoms.
Er3FeGe3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to two equivalent Ge(2) and four equivalent Ge(1) atoms. Both Er(1)-Ge(2) bond lengths are 2.94 Å. There are two shorter (2.94 Å) and two longer (3.04 Å) Er(1)-Ge(1) bond lengths. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to three equivalent Ge(2) and four equivalent Ge(1) atoms. There is one shorter (2.90 Å) and two longer (3.06 Å) Er(2)-Ge(2) bond lengths. All Er(2)-Ge(1) bond lengths are 3.03 Å. Fe(1) is bonded to four equivalent Ge(1) atoms to form distorted edge-sharing FeGe4 cuboctahedra. All Fe(1)-Ge(1) bond lengths are 2.50 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), and one Ge(2) atom. The Ge(1)-Ge(2) bond length is 2.66 Å. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to three equivalent Er(2), four equivalent Er(1), and two equivalent Ge(1) atoms.