MgYb2Cu(GeO3)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(12), one O(5), one O(7), and one O(9) atom. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(9) atom to form distorted YbO7 pentagonal bipyramids that share corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra, corners with two equivalent Ge(3)O4 tetrahedra, and  an edgeedge with one Ge(4)O4 trigonal pyramid. In the second Yb site, Yb(2) is bonded in a 7-coordinate geometry to one O(1), one O(11), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. Cu(1) is bonded in a rectangular see-saw-like geometry to one O(10), one O(11), one O(8), and one O(9) atom. There are four inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(1), one O(11), one O(5), and one O(7) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(3)O4 tetrahedra, and  a cornercorner with one Ge(4)O4 trigonal pyramid. In the second Ge site, Ge(2) is bonded to one O(10), one O(12), one O(2), and one O(6) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(3)O4 tetrahedra, and  a cornercorner with one Ge(4)O4 trigonal pyramid. In the third Ge site, Ge(3) is bonded to one O(3), one O(6), one O(7), and one O(9) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(1)O4 tetrahedra, and  a cornercorner with one Ge(2)O4 tetrahedra. In the fourth Ge site, Ge(4) is bonded to one O(12), one O(4), one O(5), and one O(8) atom to form GeO4 trigonal pyramids that share  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Ge(2)O4 tetrahedra, and  an edgeedge with one Yb(1)O7 pentagonal bipyramid. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Yb(1), one Yb(2), and one Ge(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Yb(1), one Yb(2), and one Ge(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Yb(1), one Yb(2), and one Ge(3) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Yb(1), one Yb(2), and one Ge(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Yb(1), one Ge(1), and one Ge(4) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Yb(2), one Ge(2), and one Ge(3) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ge(1), and one Ge(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Yb(2), one Cu(1), and one Ge(4) atom. In the ninth O site, O(9) is bonded in a distorted trigonal pyramidal geometry to one Mg(1), one Yb(1), one Cu(1), and one Ge(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Yb(1), one Cu(1), and one Ge(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Yb(2), one Cu(1), and one Ge(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Mg(1), one Ge(2), and one Ge(4) atom.
MgYb2Cu(GeO3)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(12), one O(5), one O(7), and one O(9) atom. The Mg(1)-O(1) bond length is 2.17 Å. The Mg(1)-O(12) bond length is 2.08 Å. The Mg(1)-O(5) bond length is 2.11 Å. The Mg(1)-O(7) bond length is 1.98 Å. The Mg(1)-O(9) bond length is 2.06 Å. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), and one O(9) atom to form distorted YbO7 pentagonal bipyramids that share corners with two equivalent Ge(1)O4 tetrahedra, corners with two equivalent Ge(2)O4 tetrahedra, corners with two equivalent Ge(3)O4 tetrahedra, and  an edgeedge with one Ge(4)O4 trigonal pyramid. The Yb(1)-O(1) bond length is 2.35 Å. The Yb(1)-O(10) bond length is 2.31 Å. The Yb(1)-O(2) bond length is 2.52 Å. The Yb(1)-O(3) bond length is 2.32 Å. The Yb(1)-O(4) bond length is 2.30 Å. The Yb(1)-O(5) bond length is 2.60 Å. The Yb(1)-O(9) bond length is 2.44 Å. In the second Yb site, Yb(2) is bonded in a 7-coordinate geometry to one O(1), one O(11), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. The Yb(2)-O(1) bond length is 2.93 Å. The Yb(2)-O(11) bond length is 2.34 Å. The Yb(2)-O(2) bond length is 2.37 Å. The Yb(2)-O(3) bond length is 2.40 Å. The Yb(2)-O(4) bond length is 2.26 Å. The Yb(2)-O(6) bond length is 2.46 Å. The Yb(2)-O(8) bond length is 2.29 Å. Cu(1) is bonded in a rectangular see-saw-like geometry to one O(10), one O(11), one O(8), and one O(9) atom. The Cu(1)-O(10) bond length is 1.92 Å. The Cu(1)-O(11) bond length is 1.99 Å. The Cu(1)-O(8) bond length is 1.94 Å. The Cu(1)-O(9) bond length is 2.12 Å. There are four inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(1), one O(11), one O(5), and one O(7) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(3)O4 tetrahedra, and  a cornercorner with one Ge(4)O4 trigonal pyramid. The Ge(1)-O(1) bond length is 1.74 Å. The Ge(1)-O(11) bond length is 1.74 Å. The Ge(1)-O(5) bond length is 1.81 Å. The Ge(1)-O(7) bond length is 1.84 Å. In the second Ge site, Ge(2) is bonded to one O(10), one O(12), one O(2), and one O(6) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(3)O4 tetrahedra, and  a cornercorner with one Ge(4)O4 trigonal pyramid. The Ge(2)-O(10) bond length is 1.76 Å. The Ge(2)-O(12) bond length is 1.84 Å. The Ge(2)-O(2) bond length is 1.73 Å. The Ge(2)-O(6) bond length is 1.80 Å. In the third Ge site, Ge(3) is bonded to one O(3), one O(6), one O(7), and one O(9) atom to form GeO4 tetrahedra that share corners with two equivalent Yb(1)O7 pentagonal bipyramids,  a cornercorner with one Ge(1)O4 tetrahedra, and  a cornercorner with one Ge(2)O4 tetrahedra. The Ge(3)-O(3) bond length is 1.71 Å. The Ge(3)-O(6) bond length is 1.81 Å. The Ge(3)-O(7) bond length is 1.82 Å. The Ge(3)-O(9) bond length is 1.79 Å. In the fourth Ge site, Ge(4) is bonded to one O(12), one O(4), one O(5), and one O(8) atom to form GeO4 trigonal pyramids that share  a cornercorner with one Ge(1)O4 tetrahedra,  a cornercorner with one Ge(2)O4 tetrahedra, and  an edgeedge with one Yb(1)O7 pentagonal bipyramid. The Ge(4)-O(12) bond length is 1.85 Å. The Ge(4)-O(4) bond length is 1.71 Å. The Ge(4)-O(5) bond length is 1.88 Å. The Ge(4)-O(8) bond length is 1.73 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Yb(1), one Yb(2), and one Ge(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Yb(1), one Yb(2), and one Ge(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Yb(1), one Yb(2), and one Ge(3) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Yb(1), one Yb(2), and one Ge(4) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Yb(1), one Ge(1), and one Ge(4) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Yb(2), one Ge(2), and one Ge(3) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ge(1), and one Ge(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Yb(2), one Cu(1), and one Ge(4) atom. In the ninth O site, O(9) is bonded in a distorted trigonal pyramidal geometry to one Mg(1), one Yb(1), one Cu(1), and one Ge(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Yb(1), one Cu(1), and one Ge(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Yb(2), one Cu(1), and one Ge(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Mg(1), one Ge(2), and one Ge(4) atom.