Tm2BaCoO5 crystallizes in the orthorhombic Pnma space group. Ba(1) is bonded in a 11-coordinate geometry to three equivalent O(3), four equivalent O(1), and four equivalent O(2) atoms. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), and four equivalent O(2) atoms. In the second Tm site, Tm(2) is bonded to one O(3), two equivalent O(2), and four equivalent O(1) atoms to form distorted TmO7 pentagonal bipyramids that share corners with five equivalent Co(1)O5 trigonal bipyramids, edges with two equivalent Tm(2)O7 pentagonal bipyramids, and  an edgeedge with one Co(1)O5 trigonal bipyramid. Co(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted CoO5 trigonal bipyramids that share corners with five equivalent Tm(2)O7 pentagonal bipyramids and  an edgeedge with one Tm(2)O7 pentagonal bipyramid. There are three inequivalent O sites. In the first O site, O(3) is bonded to three equivalent Ba(1), one Tm(1), one Tm(2), and one Co(1) atom to form distorted OBa3Tm2Co octahedra that share corners with two equivalent O(3)Ba3Tm2Co octahedra, corners with eight equivalent O(2)Ba2Tm3Co octahedra, edges with two equivalent O(3)Ba3Tm2Co octahedra, and faces with four equivalent O(2)Ba2Tm3Co octahedra. The corner-sharing octahedral tilt angles range from 1-64°. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Tm(1), two equivalent Tm(2), and one Co(1) atom. In the third O site, O(2) is bonded to two equivalent Ba(1), one Tm(2), two equivalent Tm(1), and one Co(1) atom to form distorted OBa2Tm3Co octahedra that share corners with four equivalent O(2)Ba2Tm3Co octahedra, corners with four equivalent O(3)Ba3Tm2Co octahedra, edges with two equivalent O(2)Ba2Tm3Co octahedra, faces with two equivalent O(2)Ba2Tm3Co octahedra, and faces with two equivalent O(3)Ba3Tm2Co octahedra. The corner-sharing octahedral tilt angles range from 25-78°.
Tm2BaCoO5 crystallizes in the orthorhombic Pnma space group. Ba(1) is bonded in a 11-coordinate geometry to three equivalent O(3), four equivalent O(1), and four equivalent O(2) atoms. There is one shorter (2.73 Å) and two longer (2.85 Å) Ba(1)-O(3) bond lengths. There are two shorter (3.07 Å) and two longer (3.28 Å) Ba(1)-O(1) bond lengths. There are two shorter (2.89 Å) and two longer (2.99 Å) Ba(1)-O(2) bond lengths. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), and four equivalent O(2) atoms. The Tm(1)-O(3) bond length is 2.32 Å. Both Tm(1)-O(1) bond lengths are 2.28 Å. There are two shorter (2.31 Å) and two longer (2.37 Å) Tm(1)-O(2) bond lengths. In the second Tm site, Tm(2) is bonded to one O(3), two equivalent O(2), and four equivalent O(1) atoms to form distorted TmO7 pentagonal bipyramids that share corners with five equivalent Co(1)O5 trigonal bipyramids, edges with two equivalent Tm(2)O7 pentagonal bipyramids, and  an edgeedge with one Co(1)O5 trigonal bipyramid. The Tm(2)-O(3) bond length is 2.30 Å. Both Tm(2)-O(2) bond lengths are 2.34 Å. There are two shorter (2.28 Å) and two longer (2.33 Å) Tm(2)-O(1) bond lengths. Co(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted CoO5 trigonal bipyramids that share corners with five equivalent Tm(2)O7 pentagonal bipyramids and  an edgeedge with one Tm(2)O7 pentagonal bipyramid. The Co(1)-O(3) bond length is 2.00 Å. Both Co(1)-O(1) bond lengths are 2.04 Å. Both Co(1)-O(2) bond lengths are 2.11 Å. There are three inequivalent O sites. In the first O site, O(3) is bonded to three equivalent Ba(1), one Tm(1), one Tm(2), and one Co(1) atom to form distorted OBa3Tm2Co octahedra that share corners with two equivalent O(3)Ba3Tm2Co octahedra, corners with eight equivalent O(2)Ba2Tm3Co octahedra, edges with two equivalent O(3)Ba3Tm2Co octahedra, and faces with four equivalent O(2)Ba2Tm3Co octahedra. The corner-sharing octahedral tilt angles range from 1-64°. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Tm(1), two equivalent Tm(2), and one Co(1) atom. In the third O site, O(2) is bonded to two equivalent Ba(1), one Tm(2), two equivalent Tm(1), and one Co(1) atom to form distorted OBa2Tm3Co octahedra that share corners with four equivalent O(2)Ba2Tm3Co octahedra, corners with four equivalent O(3)Ba3Tm2Co octahedra, edges with two equivalent O(2)Ba2Tm3Co octahedra, faces with two equivalent O(2)Ba2Tm3Co octahedra, and faces with two equivalent O(3)Ba3Tm2Co octahedra. The corner-sharing octahedral tilt angles range from 25-78°.