Ba2MgLaBiO6 crystallizes in the monoclinic Cm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and four equivalent O(1) atoms. Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO5 square pyramids that share corners with two equivalent La(1)O6 octahedra and  a faceface with one La(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. La(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted LaO6 octahedra that share corners with two equivalent Mg(1)O5 square pyramids and  a faceface with one Mg(1)O5 square pyramid. Bi(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(1), two equivalent Ba(2), one Mg(1), one La(1), and one Bi(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(2), one Mg(1), one La(1), and one Bi(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ba(2), two equivalent Ba(1), one La(1), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), two equivalent Ba(2), one Mg(1), and one La(1) atom.
Ba2MgLaBiO6 crystallizes in the monoclinic Cm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Ba(1)-O(4) bond length is 2.44 Å. Both Ba(1)-O(1) bond lengths are 2.67 Å. Both Ba(1)-O(2) bond lengths are 2.91 Å. Both Ba(1)-O(3) bond lengths are 3.27 Å. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(3), two equivalent O(2), two equivalent O(4), and four equivalent O(1) atoms. The Ba(2)-O(3) bond length is 2.65 Å. Both Ba(2)-O(2) bond lengths are 2.74 Å. Both Ba(2)-O(4) bond lengths are 3.19 Å. There are two shorter (3.04 Å) and two longer (3.31 Å) Ba(2)-O(1) bond lengths. Mg(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO5 square pyramids that share corners with two equivalent La(1)O6 octahedra and  a faceface with one La(1)O6 octahedra. The corner-sharing octahedral tilt angles are 36°. The Mg(1)-O(4) bond length is 1.98 Å. Both Mg(1)-O(1) bond lengths are 2.11 Å. Both Mg(1)-O(2) bond lengths are 2.22 Å. La(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted LaO6 octahedra that share corners with two equivalent Mg(1)O5 square pyramids and  a faceface with one Mg(1)O5 square pyramid. The La(1)-O(3) bond length is 2.36 Å. The La(1)-O(4) bond length is 2.32 Å. Both La(1)-O(1) bond lengths are 2.74 Å. Both La(1)-O(2) bond lengths are 2.36 Å. Bi(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. The Bi(1)-O(3) bond length is 2.19 Å. Both Bi(1)-O(1) bond lengths are 2.49 Å. Both Bi(1)-O(2) bond lengths are 2.45 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(1), two equivalent Ba(2), one Mg(1), one La(1), and one Bi(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(2), one Mg(1), one La(1), and one Bi(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ba(2), two equivalent Ba(1), one La(1), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), two equivalent Ba(2), one Mg(1), and one La(1) atom.