MgYb5 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 10-coordinate geometry to one Yb(3), two equivalent Yb(1), two equivalent Yb(2), two equivalent Yb(4), and three equivalent Yb(5) atoms. There are five inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 2-coordinate geometry to two equivalent Mg(1), two equivalent Yb(3), two equivalent Yb(5), and three equivalent Yb(2) atoms. In the second Yb site, Yb(2) is bonded to two equivalent Mg(1), one Yb(5), two equivalent Yb(2), two equivalent Yb(3), two equivalent Yb(4), and three equivalent Yb(1) atoms to form distorted YbYb10Mg2 cuboctahedra that share corners with six equivalent Yb(2)Yb10Mg2 cuboctahedra, edges with four equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with six equivalent Yb(3)Yb11Mg cuboctahedra, faces with two equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with three equivalent Yb(3)Yb11Mg cuboctahedra, and faces with four equivalent Yb(5)Yb9Mg3 cuboctahedra. In the third Yb site, Yb(3) is bonded to one Mg(1), two equivalent Yb(1), two equivalent Yb(2), two equivalent Yb(3), two equivalent Yb(5), and three equivalent Yb(4) atoms to form YbYb11Mg cuboctahedra that share corners with six equivalent Yb(3)Yb11Mg cuboctahedra, corners with six equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with three equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with six equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with two equivalent Yb(3)Yb11Mg cuboctahedra, faces with three equivalent Yb(2)Yb10Mg2 cuboctahedra, and faces with three equivalent Yb(5)Yb9Mg3 cuboctahedra. In the fourth Yb site, Yb(4) is bonded in a 2-coordinate geometry to two equivalent Mg(1), two equivalent Yb(2), two equivalent Yb(5), and three equivalent Yb(3) atoms. In the fifth Yb site, Yb(5) is bonded to three equivalent Mg(1), one Yb(2), two equivalent Yb(1), two equivalent Yb(3), two equivalent Yb(4), and two equivalent Yb(5) atoms to form distorted YbYb9Mg3 cuboctahedra that share corners with six equivalent Yb(3)Yb11Mg cuboctahedra, corners with six equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with three equivalent Yb(3)Yb11Mg cuboctahedra, edges with four equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with two equivalent Yb(5)Yb9Mg3 cuboctahedra, faces with three equivalent Yb(3)Yb11Mg cuboctahedra, and faces with four equivalent Yb(2)Yb10Mg2 cuboctahedra.
MgYb5 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 10-coordinate geometry to one Yb(3), two equivalent Yb(1), two equivalent Yb(2), two equivalent Yb(4), and three equivalent Yb(5) atoms. The Mg(1)-Yb(3) bond length is 3.72 Å. Both Mg(1)-Yb(1) bond lengths are 3.52 Å. Both Mg(1)-Yb(2) bond lengths are 3.62 Å. Both Mg(1)-Yb(4) bond lengths are 3.53 Å. There are two shorter (3.55 Å) and one longer (3.97 Å) Mg(1)-Yb(5) bond length. There are five inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 2-coordinate geometry to two equivalent Mg(1), two equivalent Yb(3), two equivalent Yb(5), and three equivalent Yb(2) atoms. Both Yb(1)-Yb(3) bond lengths are 3.73 Å. Both Yb(1)-Yb(5) bond lengths are 3.69 Å. There is one shorter (3.65 Å) and two longer (3.85 Å) Yb(1)-Yb(2) bond lengths. In the second Yb site, Yb(2) is bonded to two equivalent Mg(1), one Yb(5), two equivalent Yb(2), two equivalent Yb(3), two equivalent Yb(4), and three equivalent Yb(1) atoms to form distorted YbYb10Mg2 cuboctahedra that share corners with six equivalent Yb(2)Yb10Mg2 cuboctahedra, edges with four equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with six equivalent Yb(3)Yb11Mg cuboctahedra, faces with two equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with three equivalent Yb(3)Yb11Mg cuboctahedra, and faces with four equivalent Yb(5)Yb9Mg3 cuboctahedra. The Yb(2)-Yb(5) bond length is 3.57 Å. Both Yb(2)-Yb(2) bond lengths are 3.79 Å. Both Yb(2)-Yb(3) bond lengths are 3.79 Å. Both Yb(2)-Yb(4) bond lengths are 3.89 Å. In the third Yb site, Yb(3) is bonded to one Mg(1), two equivalent Yb(1), two equivalent Yb(2), two equivalent Yb(3), two equivalent Yb(5), and three equivalent Yb(4) atoms to form YbYb11Mg cuboctahedra that share corners with six equivalent Yb(3)Yb11Mg cuboctahedra, corners with six equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with three equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with six equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with two equivalent Yb(3)Yb11Mg cuboctahedra, faces with three equivalent Yb(2)Yb10Mg2 cuboctahedra, and faces with three equivalent Yb(5)Yb9Mg3 cuboctahedra. Both Yb(3)-Yb(3) bond lengths are 3.79 Å. Both Yb(3)-Yb(5) bond lengths are 3.64 Å. There are two shorter (3.70 Å) and one longer (3.87 Å) Yb(3)-Yb(4) bond length. In the fourth Yb site, Yb(4) is bonded in a 2-coordinate geometry to two equivalent Mg(1), two equivalent Yb(2), two equivalent Yb(5), and three equivalent Yb(3) atoms. Both Yb(4)-Yb(5) bond lengths are 3.74 Å. In the fifth Yb site, Yb(5) is bonded to three equivalent Mg(1), one Yb(2), two equivalent Yb(1), two equivalent Yb(3), two equivalent Yb(4), and two equivalent Yb(5) atoms to form distorted YbYb9Mg3 cuboctahedra that share corners with six equivalent Yb(3)Yb11Mg cuboctahedra, corners with six equivalent Yb(5)Yb9Mg3 cuboctahedra, edges with three equivalent Yb(3)Yb11Mg cuboctahedra, edges with four equivalent Yb(2)Yb10Mg2 cuboctahedra, faces with two equivalent Yb(5)Yb9Mg3 cuboctahedra, faces with three equivalent Yb(3)Yb11Mg cuboctahedra, and faces with four equivalent Yb(2)Yb10Mg2 cuboctahedra. Both Yb(5)-Yb(5) bond lengths are 3.79 Å.