MgLa5 crystallizes in the trigonal R32 space group. Mg(1) is bonded to six equivalent La(1) and six equivalent La(2) atoms to form MgLa12 cuboctahedra that share corners with six equivalent Mg(1)La12 cuboctahedra, corners with twelve equivalent La(2)La9Mg3 cuboctahedra, edges with six equivalent Mg(1)La12 cuboctahedra, and faces with eight equivalent La(2)La9Mg3 cuboctahedra. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to two equivalent Mg(1), four equivalent La(1), and four equivalent La(2) atoms. In the second La site, La(2) is bonded to three equivalent Mg(1), three equivalent La(2), and six equivalent La(1) atoms to form distorted LaLa9Mg3 cuboctahedra that share corners with six equivalent Mg(1)La12 cuboctahedra, corners with twelve equivalent La(2)La9Mg3 cuboctahedra, edges with six equivalent La(2)La9Mg3 cuboctahedra, faces with four equivalent Mg(1)La12 cuboctahedra, and faces with four equivalent La(2)La9Mg3 cuboctahedra.
MgLa5 crystallizes in the trigonal R32 space group. Mg(1) is bonded to six equivalent La(1) and six equivalent La(2) atoms to form MgLa12 cuboctahedra that share corners with six equivalent Mg(1)La12 cuboctahedra, corners with twelve equivalent La(2)La9Mg3 cuboctahedra, edges with six equivalent Mg(1)La12 cuboctahedra, and faces with eight equivalent La(2)La9Mg3 cuboctahedra. All Mg(1)-La(1) bond lengths are 3.54 Å. All Mg(1)-La(2) bond lengths are 3.73 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to two equivalent Mg(1), four equivalent La(1), and four equivalent La(2) atoms. All La(1)-La(1) bond lengths are 3.49 Å. There are two shorter (3.62 Å) and two longer (3.74 Å) La(1)-La(2) bond lengths. In the second La site, La(2) is bonded to three equivalent Mg(1), three equivalent La(2), and six equivalent La(1) atoms to form distorted LaLa9Mg3 cuboctahedra that share corners with six equivalent Mg(1)La12 cuboctahedra, corners with twelve equivalent La(2)La9Mg3 cuboctahedra, edges with six equivalent La(2)La9Mg3 cuboctahedra, faces with four equivalent Mg(1)La12 cuboctahedra, and faces with four equivalent La(2)La9Mg3 cuboctahedra. All La(2)-La(2) bond lengths are 3.76 Å.