Er2AlGe3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 11-coordinate geometry to two equivalent Al(1), one Ge(1), four equivalent Ge(2), and four equivalent Ge(3) atoms. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to two equivalent Ge(2), two equivalent Ge(3), and three equivalent Ge(1) atoms. Al(1) is bonded to two equivalent Er(1), one Ge(3), and three equivalent Ge(1) atoms to form distorted AlEr2Ge4 tetrahedra that share corners with two equivalent Ge(1)Er4Al3 pentagonal bipyramids and edges with four equivalent Al(1)Er2Ge4 tetrahedra. There are three inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Er(1), three equivalent Er(2), and three equivalent Al(1) atoms to form distorted GeEr4Al3 pentagonal bipyramids that share corners with two equivalent Al(1)Er2Ge4 tetrahedra and edges with six equivalent Ge(1)Er4Al3 pentagonal bipyramids. In the second Ge site, Ge(2) is bonded in a 8-coordinate geometry to two equivalent Er(2), four equivalent Er(1), and two equivalent Ge(3) atoms. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to two equivalent Er(2), four equivalent Er(1), one Al(1), and two equivalent Ge(2) atoms.
Er2AlGe3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 11-coordinate geometry to two equivalent Al(1), one Ge(1), four equivalent Ge(2), and four equivalent Ge(3) atoms. Both Er(1)-Al(1) bond lengths are 3.31 Å. The Er(1)-Ge(1) bond length is 3.02 Å. There are two shorter (2.96 Å) and two longer (3.33 Å) Er(1)-Ge(2) bond lengths. There are two shorter (2.99 Å) and two longer (3.11 Å) Er(1)-Ge(3) bond lengths. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to two equivalent Ge(2), two equivalent Ge(3), and three equivalent Ge(1) atoms. Both Er(2)-Ge(2) bond lengths are 2.93 Å. Both Er(2)-Ge(3) bond lengths are 3.04 Å. There is one shorter (2.98 Å) and two longer (3.02 Å) Er(2)-Ge(1) bond lengths. Al(1) is bonded to two equivalent Er(1), one Ge(3), and three equivalent Ge(1) atoms to form distorted AlEr2Ge4 tetrahedra that share corners with two equivalent Ge(1)Er4Al3 pentagonal bipyramids and edges with four equivalent Al(1)Er2Ge4 tetrahedra. The Al(1)-Ge(3) bond length is 2.56 Å. There are two shorter (2.55 Å) and one longer (2.70 Å) Al(1)-Ge(1) bond length. There are three inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Er(1), three equivalent Er(2), and three equivalent Al(1) atoms to form distorted GeEr4Al3 pentagonal bipyramids that share corners with two equivalent Al(1)Er2Ge4 tetrahedra and edges with six equivalent Ge(1)Er4Al3 pentagonal bipyramids. In the second Ge site, Ge(2) is bonded in a 8-coordinate geometry to two equivalent Er(2), four equivalent Er(1), and two equivalent Ge(3) atoms. There is one shorter (2.57 Å) and one longer (2.68 Å) Ge(2)-Ge(3) bond length. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to two equivalent Er(2), four equivalent Er(1), one Al(1), and two equivalent Ge(2) atoms.