BaErMn2O5 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a distorted body-centered cubic geometry to eight equivalent O(1) atoms. Er(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form ErO12 cuboctahedra that share corners with four equivalent Er(1)O12 cuboctahedra, faces with four equivalent Er(1)O12 cuboctahedra, and faces with eight equivalent Mn(1)O5 square pyramids. Mn(1) is bonded to one O(2) and four equivalent O(1) atoms to form MnO5 square pyramids that share corners with five equivalent Mn(1)O5 square pyramids and faces with four equivalent Er(1)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Er(1), and two equivalent Mn(1) atoms to form a mixture of distorted corner, face, and edge-sharing OBa2Er2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Er(1) and two equivalent Mn(1) atoms.
BaErMn2O5 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded in a distorted body-centered cubic geometry to eight equivalent O(1) atoms. All Ba(1)-O(1) bond lengths are 2.80 Å. Er(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form ErO12 cuboctahedra that share corners with four equivalent Er(1)O12 cuboctahedra, faces with four equivalent Er(1)O12 cuboctahedra, and faces with eight equivalent Mn(1)O5 square pyramids. All Er(1)-O(2) bond lengths are 2.81 Å. All Er(1)-O(1) bond lengths are 2.75 Å. Mn(1) is bonded to one O(2) and four equivalent O(1) atoms to form MnO5 square pyramids that share corners with five equivalent Mn(1)O5 square pyramids and faces with four equivalent Er(1)O12 cuboctahedra. The Mn(1)-O(2) bond length is 1.92 Å. All Mn(1)-O(1) bond lengths are 1.99 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Er(1), and two equivalent Mn(1) atoms to form a mixture of distorted corner, face, and edge-sharing OBa2Er2Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Er(1) and two equivalent Mn(1) atoms.