MgTm3 crystallizes in the tetragonal P4/mmm space group. Mg(1) is bonded in a distorted body-centered cubic geometry to eight equivalent Tm(1) atoms. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to four equivalent Mg(1), four equivalent Tm(1), and four equivalent Tm(2) atoms to form distorted TmTm8Mg4 cuboctahedra that share corners with twelve equivalent Tm(1)Tm8Mg4 cuboctahedra, edges with eight equivalent Tm(2)Tm12 cuboctahedra, edges with eight equivalent Tm(1)Tm8Mg4 cuboctahedra, faces with four equivalent Tm(2)Tm12 cuboctahedra, and faces with ten equivalent Tm(1)Tm8Mg4 cuboctahedra. In the second Tm site, Tm(2) is bonded to four equivalent Tm(2) and eight equivalent Tm(1) atoms to form TmTm12 cuboctahedra that share corners with four equivalent Tm(2)Tm12 cuboctahedra, edges with sixteen equivalent Tm(1)Tm8Mg4 cuboctahedra, faces with eight equivalent Tm(2)Tm12 cuboctahedra, and faces with eight equivalent Tm(1)Tm8Mg4 cuboctahedra.
MgTm3 crystallizes in the tetragonal P4/mmm space group. Mg(1) is bonded in a distorted body-centered cubic geometry to eight equivalent Tm(1) atoms. All Mg(1)-Tm(1) bond lengths are 3.31 Å. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to four equivalent Mg(1), four equivalent Tm(1), and four equivalent Tm(2) atoms to form distorted TmTm8Mg4 cuboctahedra that share corners with twelve equivalent Tm(1)Tm8Mg4 cuboctahedra, edges with eight equivalent Tm(2)Tm12 cuboctahedra, edges with eight equivalent Tm(1)Tm8Mg4 cuboctahedra, faces with four equivalent Tm(2)Tm12 cuboctahedra, and faces with ten equivalent Tm(1)Tm8Mg4 cuboctahedra. All Tm(1)-Tm(1) bond lengths are 3.52 Å. All Tm(1)-Tm(2) bond lengths are 3.47 Å. In the second Tm site, Tm(2) is bonded to four equivalent Tm(2) and eight equivalent Tm(1) atoms to form TmTm12 cuboctahedra that share corners with four equivalent Tm(2)Tm12 cuboctahedra, edges with sixteen equivalent Tm(1)Tm8Mg4 cuboctahedra, faces with eight equivalent Tm(2)Tm12 cuboctahedra, and faces with eight equivalent Tm(1)Tm8Mg4 cuboctahedra. All Tm(2)-Tm(2) bond lengths are 3.52 Å.