MgEr4Ge4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a 5-coordinate geometry to one Ge(1), two equivalent Ge(2), and two equivalent Ge(3) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one Ge(1), two equivalent Ge(3), and four equivalent Ge(2) atoms. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to one Ge(3), two equivalent Ge(1), and three equivalent Ge(2) atoms. There are three inequivalent Ge sites. In the first Ge site, Ge(3) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Er(2), four equivalent Er(1), and one Ge(1) atom. In the second Ge site, Ge(1) is bonded in a 8-coordinate geometry to one Mg(1), two equivalent Er(1), four equivalent Er(2), and one Ge(3) atom. In the third Ge site, Ge(2) is bonded in a 9-coordinate geometry to one Mg(1), three equivalent Er(2), four equivalent Er(1), and one Ge(2) atom.
MgEr4Ge4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded in a 5-coordinate geometry to one Ge(1), two equivalent Ge(2), and two equivalent Ge(3) atoms. The Mg(1)-Ge(1) bond length is 2.74 Å. Both Mg(1)-Ge(2) bond lengths are 3.12 Å. There is one shorter (2.82 Å) and one longer (2.83 Å) Mg(1)-Ge(3) bond length. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one Ge(1), two equivalent Ge(3), and four equivalent Ge(2) atoms. The Er(1)-Ge(1) bond length is 3.10 Å. There is one shorter (3.01 Å) and one longer (3.12 Å) Er(1)-Ge(3) bond length. There are a spread of Er(1)-Ge(2) bond distances ranging from 2.96-3.27 Å. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to one Ge(3), two equivalent Ge(1), and three equivalent Ge(2) atoms. The Er(2)-Ge(3) bond length is 3.04 Å. There is one shorter (2.88 Å) and one longer (2.90 Å) Er(2)-Ge(1) bond length. There are a spread of Er(2)-Ge(2) bond distances ranging from 2.82-2.99 Å. There are three inequivalent Ge sites. In the first Ge site, Ge(3) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Er(2), four equivalent Er(1), and one Ge(1) atom. The Ge(3)-Ge(1) bond length is 2.60 Å. In the second Ge site, Ge(1) is bonded in a 8-coordinate geometry to one Mg(1), two equivalent Er(1), four equivalent Er(2), and one Ge(3) atom. In the third Ge site, Ge(2) is bonded in a 9-coordinate geometry to one Mg(1), three equivalent Er(2), four equivalent Er(1), and one Ge(2) atom. The Ge(2)-Ge(2) bond length is 2.73 Å.