Er3Ge4 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to two equivalent Ge(2), two equivalent Ge(3), 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. There are three 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), one Ge(2), and two equivalent Ge(3) atoms. 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. In the third Ge site, Ge(3) is bonded in a 4-coordinate geometry to four equivalent Er(1) and four equivalent Ge(1) atoms.
Er3Ge4 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to two equivalent Ge(2), two equivalent Ge(3), and four equivalent Ge(1) atoms. Both Er(1)-Ge(2) bond lengths are 3.01 Å. Both Er(1)-Ge(3) bond lengths are 3.01 Å. There are a spread of Er(1)-Ge(1) bond distances ranging from 2.94-3.06 Å. 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 (2.86 Å) and two longer (3.14 Å) Er(2)-Ge(2) bond lengths. All Er(2)-Ge(1) bond lengths are 2.93 Å. There are three 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), one Ge(2), and two equivalent Ge(3) atoms. The Ge(1)-Ge(2) bond length is 2.58 Å. Both Ge(1)-Ge(3) bond lengths are 2.83 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. In the third Ge site, Ge(3) is bonded in a 4-coordinate geometry to four equivalent Er(1) and four equivalent Ge(1) atoms.