YAlMgGe2 crystallizes in the trigonal P3m1 space group. Mg(1) is bonded to one Ge(2) and three equivalent Ge(1) atoms to form distorted MgGe4 tetrahedra that share corners with six equivalent Y(1)Ge6 octahedra, corners with six equivalent Mg(1)Ge4 tetrahedra, edges with three equivalent Y(1)Ge6 octahedra, and edges with three equivalent Al(1)Ge4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-56°. Y(1) is bonded to three equivalent Ge(1) and three equivalent Ge(2) atoms to form YGe6 octahedra that share corners with six equivalent Mg(1)Ge4 tetrahedra, corners with six equivalent Al(1)Ge4 tetrahedra, edges with six equivalent Y(1)Ge6 octahedra, edges with three equivalent Mg(1)Ge4 tetrahedra, and edges with three equivalent Al(1)Ge4 tetrahedra. Al(1) is bonded to one Ge(1) and three equivalent Ge(2) atoms to form distorted AlGe4 tetrahedra that share corners with six equivalent Y(1)Ge6 octahedra, corners with six equivalent Al(1)Ge4 tetrahedra, edges with three equivalent Y(1)Ge6 octahedra, and edges with three equivalent Mg(1)Ge4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-57°. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to three equivalent Mg(1), three equivalent Y(1), and one Al(1) atom to form distorted GeY3Mg3Al pentagonal bipyramids that share corners with three equivalent Ge(2)Y3MgAl3 pentagonal bipyramids, edges with six equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, and edges with six equivalent Ge(2)Y3MgAl3 pentagonal bipyramids. In the second Ge site, Ge(2) is bonded to one Mg(1), three equivalent Y(1), and three equivalent Al(1) atoms to form distorted GeY3MgAl3 pentagonal bipyramids that share corners with three equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, edges with six equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, and edges with six equivalent Ge(2)Y3MgAl3 pentagonal bipyramids.
YAlMgGe2 crystallizes in the trigonal P3m1 space group. Mg(1) is bonded to one Ge(2) and three equivalent Ge(1) atoms to form distorted MgGe4 tetrahedra that share corners with six equivalent Y(1)Ge6 octahedra, corners with six equivalent Mg(1)Ge4 tetrahedra, edges with three equivalent Y(1)Ge6 octahedra, and edges with three equivalent Al(1)Ge4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-56°. The Mg(1)-Ge(2) bond length is 2.74 Å. All Mg(1)-Ge(1) bond lengths are 2.62 Å. Y(1) is bonded to three equivalent Ge(1) and three equivalent Ge(2) atoms to form YGe6 octahedra that share corners with six equivalent Mg(1)Ge4 tetrahedra, corners with six equivalent Al(1)Ge4 tetrahedra, edges with six equivalent Y(1)Ge6 octahedra, edges with three equivalent Mg(1)Ge4 tetrahedra, and edges with three equivalent Al(1)Ge4 tetrahedra. All Y(1)-Ge(1) bond lengths are 2.98 Å. All Y(1)-Ge(2) bond lengths are 3.01 Å. Al(1) is bonded to one Ge(1) and three equivalent Ge(2) atoms to form distorted AlGe4 tetrahedra that share corners with six equivalent Y(1)Ge6 octahedra, corners with six equivalent Al(1)Ge4 tetrahedra, edges with three equivalent Y(1)Ge6 octahedra, and edges with three equivalent Mg(1)Ge4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-57°. The Al(1)-Ge(1) bond length is 2.65 Å. All Al(1)-Ge(2) bond lengths are 2.64 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to three equivalent Mg(1), three equivalent Y(1), and one Al(1) atom to form distorted GeY3Mg3Al pentagonal bipyramids that share corners with three equivalent Ge(2)Y3MgAl3 pentagonal bipyramids, edges with six equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, and edges with six equivalent Ge(2)Y3MgAl3 pentagonal bipyramids. In the second Ge site, Ge(2) is bonded to one Mg(1), three equivalent Y(1), and three equivalent Al(1) atoms to form distorted GeY3MgAl3 pentagonal bipyramids that share corners with three equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, edges with six equivalent Ge(1)Y3Mg3Al pentagonal bipyramids, and edges with six equivalent Ge(2)Y3MgAl3 pentagonal bipyramids.