U2Co3O8 crystallizes in the monoclinic Pm space group. There are four inequivalent U sites. In the first U site, U(1) is bonded to one O(6), one O(9), two equivalent O(3), and two equivalent O(4) atoms to form distorted UO6 pentagonal pyramids that share edges with two equivalent Co(2)O4 trigonal pyramids. In the second U site, U(2) is bonded to one O(11), one O(12), two equivalent O(1), and two equivalent O(2) atoms to form distorted UO6 pentagonal pyramids that share corners with two equivalent Co(2)O4 trigonal pyramids. In the third U site, U(3) is bonded in a 6-coordinate geometry to one O(10), one O(7), two equivalent O(1), and two equivalent O(2) atoms. In the fourth U site, U(4) is bonded in a 6-coordinate geometry to one O(5), one O(8), two equivalent O(3), and two equivalent O(4) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a distorted T-shaped geometry to one O(12), one O(2), and one O(3) atom. In the second Co site, Co(2) is bonded to one O(1), one O(10), one O(4), and one O(9) atom to form distorted CoO4 trigonal pyramids that share  a cornercorner with one U(2)O6 pentagonal pyramid,  an edgeedge with one U(1)O6 pentagonal pyramid, and  an edgeedge with one Co(2)O4 trigonal pyramid. In the third Co site, Co(3) is bonded in a trigonal planar geometry to one O(10), one O(7), and one O(9) atom. In the fourth Co site, Co(4) is bonded in a linear geometry to one O(12) and one O(8) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one U(2), one U(3), and one Co(2) atom. In the second O site, O(2) is bonded in a trigonal non-coplanar geometry to one U(2), one U(3), and one Co(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one U(1), one U(4), and one Co(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one U(1), one U(4), and one Co(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one U(4) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(1) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one U(3) and one Co(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to one U(4) and one Co(4) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one Co(3), and two equivalent Co(2) atoms. In the tenth O site, O(10) is bonded in a distorted trigonal pyramidal geometry to one U(3), one Co(3), and two equivalent Co(2) atoms. In the eleventh O site, O(11) is bonded in a single-bond geometry to one U(2) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one U(2), one Co(4), and two equivalent Co(1) atoms.
U2Co3O8 crystallizes in the monoclinic Pm space group. There are four inequivalent U sites. In the first U site, U(1) is bonded to one O(6), one O(9), two equivalent O(3), and two equivalent O(4) atoms to form distorted UO6 pentagonal pyramids that share edges with two equivalent Co(2)O4 trigonal pyramids. The U(1)-O(6) bond length is 1.87 Å. The U(1)-O(9) bond length is 2.49 Å. Both U(1)-O(3) bond lengths are 2.15 Å. Both U(1)-O(4) bond lengths are 2.25 Å. In the second U site, U(2) is bonded to one O(11), one O(12), two equivalent O(1), and two equivalent O(2) atoms to form distorted UO6 pentagonal pyramids that share corners with two equivalent Co(2)O4 trigonal pyramids. The U(2)-O(11) bond length is 1.88 Å. The U(2)-O(12) bond length is 2.33 Å. Both U(2)-O(1) bond lengths are 2.12 Å. Both U(2)-O(2) bond lengths are 2.44 Å. In the third U site, U(3) is bonded in a 6-coordinate geometry to one O(10), one O(7), two equivalent O(1), and two equivalent O(2) atoms. The U(3)-O(10) bond length is 2.30 Å. The U(3)-O(7) bond length is 2.00 Å. Both U(3)-O(1) bond lengths are 2.42 Å. Both U(3)-O(2) bond lengths are 2.09 Å. In the fourth U site, U(4) is bonded in a 6-coordinate geometry to one O(5), one O(8), two equivalent O(3), and two equivalent O(4) atoms. The U(4)-O(5) bond length is 1.82 Å. The U(4)-O(8) bond length is 1.91 Å. Both U(4)-O(3) bond lengths are 2.42 Å. Both U(4)-O(4) bond lengths are 2.20 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a distorted T-shaped geometry to one O(12), one O(2), and one O(3) atom. The Co(1)-O(12) bond length is 2.20 Å. The Co(1)-O(2) bond length is 1.89 Å. The Co(1)-O(3) bond length is 1.84 Å. In the second Co site, Co(2) is bonded to one O(1), one O(10), one O(4), and one O(9) atom to form distorted CoO4 trigonal pyramids that share  a cornercorner with one U(2)O6 pentagonal pyramid,  an edgeedge with one U(1)O6 pentagonal pyramid, and  an edgeedge with one Co(2)O4 trigonal pyramid. The Co(2)-O(1) bond length is 1.94 Å. The Co(2)-O(10) bond length is 2.05 Å. The Co(2)-O(4) bond length is 1.94 Å. The Co(2)-O(9) bond length is 2.00 Å. In the third Co site, Co(3) is bonded in a trigonal planar geometry to one O(10), one O(7), and one O(9) atom. The Co(3)-O(10) bond length is 1.87 Å. The Co(3)-O(7) bond length is 1.92 Å. The Co(3)-O(9) bond length is 1.82 Å. In the fourth Co site, Co(4) is bonded in a linear geometry to one O(12) and one O(8) atom. The Co(4)-O(12) bond length is 1.79 Å. The Co(4)-O(8) bond length is 1.82 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one U(2), one U(3), and one Co(2) atom. In the second O site, O(2) is bonded in a trigonal non-coplanar geometry to one U(2), one U(3), and one Co(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one U(1), one U(4), and one Co(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one U(1), one U(4), and one Co(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one U(4) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one U(1) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one U(3) and one Co(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to one U(4) and one Co(4) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one Co(3), and two equivalent Co(2) atoms. In the tenth O site, O(10) is bonded in a distorted trigonal pyramidal geometry to one U(3), one Co(3), and two equivalent Co(2) atoms. In the eleventh O site, O(11) is bonded in a single-bond geometry to one U(2) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one U(2), one Co(4), and two equivalent Co(1) atoms.