Be13Tm crystallizes in the cubic Fm-3c space group. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded to twelve equivalent Be(2) atoms to form a mixture of face and corner-sharing BeBe12 cuboctahedra. In the second Be site, Be(2) is bonded to one Be(1), nine equivalent Be(2), and two equivalent Tm(1) atoms to form distorted BeTm2Be10 cuboctahedra that share  a cornercorner with one Be(1)Be12 cuboctahedra, corners with twenty-seven equivalent Be(2)Tm2Be10 cuboctahedra, edges with eight equivalent Be(2)Tm2Be10 cuboctahedra, faces with two equivalent Be(1)Be12 cuboctahedra, and faces with twenty-three equivalent Be(2)Tm2Be10 cuboctahedra. Tm(1) is bonded in a 24-coordinate geometry to twenty-four equivalent Be(2) atoms.
Be13Tm crystallizes in the cubic Fm-3c space group. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded to twelve equivalent Be(2) atoms to form a mixture of face and corner-sharing BeBe12 cuboctahedra. All Be(1)-Be(2) bond lengths are 2.13 Å. In the second Be site, Be(2) is bonded to one Be(1), nine equivalent Be(2), and two equivalent Tm(1) atoms to form distorted BeTm2Be10 cuboctahedra that share  a cornercorner with one Be(1)Be12 cuboctahedra, corners with twenty-seven equivalent Be(2)Tm2Be10 cuboctahedra, edges with eight equivalent Be(2)Tm2Be10 cuboctahedra, faces with two equivalent Be(1)Be12 cuboctahedra, and faces with twenty-three equivalent Be(2)Tm2Be10 cuboctahedra. There are eight shorter (2.22 Å) and one longer (2.32 Å) Be(2)-Be(2) bond length. Both Be(2)-Tm(1) bond lengths are 2.98 Å. Tm(1) is bonded in a 24-coordinate geometry to twenty-four equivalent Be(2) atoms.