YMnFeO5 crystallizes in the orthorhombic Pbam space group. Y(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), and four equivalent O(3) atoms. Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Fe(1)O5 square pyramids and edges with two equivalent Mn(1)O6 octahedra. Fe(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form FeO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  an edgeedge with one Fe(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 50-55°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Fe(1) atoms to form distorted OY2Fe2 trigonal pyramids that share corners with eight equivalent O(3)Y2MnFe tetrahedra, corners with four equivalent O(4)Y2Mn2 trigonal pyramids, edges with two equivalent O(3)Y2MnFe tetrahedra, and edges with two equivalent O(1)Y2Fe2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one Fe(1) atom. In the third O site, O(3) is bonded to two equivalent Y(1), one Mn(1), and one Fe(1) atom to form distorted OY2MnFe tetrahedra that share corners with six equivalent O(3)Y2MnFe tetrahedra, corners with two equivalent O(4)Y2Mn2 trigonal pyramids, corners with four equivalent O(1)Y2Fe2 trigonal pyramids,  an edgeedge with one O(3)Y2MnFe tetrahedra,  an edgeedge with one O(1)Y2Fe2 trigonal pyramid, and edges with two equivalent O(4)Y2Mn2 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Mn(1) atoms to form distorted OY2Mn2 trigonal pyramids that share corners with four equivalent O(3)Y2MnFe tetrahedra, corners with two equivalent O(4)Y2Mn2 trigonal pyramids, corners with four equivalent O(1)Y2Fe2 trigonal pyramids, edges with four equivalent O(3)Y2MnFe tetrahedra, and  an edgeedge with one O(4)Y2Mn2 trigonal pyramid.
YMnFeO5 crystallizes in the orthorhombic Pbam space group. Y(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), and four equivalent O(3) atoms. Both Y(1)-O(1) bond lengths are 2.34 Å. There is one shorter (2.37 Å) and one longer (2.48 Å) Y(1)-O(4) bond length. There are two shorter (2.39 Å) and two longer (2.50 Å) Y(1)-O(3) bond lengths. Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Fe(1)O5 square pyramids and edges with two equivalent Mn(1)O6 octahedra. Both Mn(1)-O(2) bond lengths are 1.93 Å. Both Mn(1)-O(3) bond lengths are 1.93 Å. Both Mn(1)-O(4) bond lengths are 1.94 Å. Fe(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form FeO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  an edgeedge with one Fe(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 50-55°. The Fe(1)-O(2) bond length is 1.90 Å. Both Fe(1)-O(1) bond lengths are 2.01 Å. Both Fe(1)-O(3) bond lengths are 1.98 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Fe(1) atoms to form distorted OY2Fe2 trigonal pyramids that share corners with eight equivalent O(3)Y2MnFe tetrahedra, corners with four equivalent O(4)Y2Mn2 trigonal pyramids, edges with two equivalent O(3)Y2MnFe tetrahedra, and edges with two equivalent O(1)Y2Fe2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one Fe(1) atom. In the third O site, O(3) is bonded to two equivalent Y(1), one Mn(1), and one Fe(1) atom to form distorted OY2MnFe tetrahedra that share corners with six equivalent O(3)Y2MnFe tetrahedra, corners with two equivalent O(4)Y2Mn2 trigonal pyramids, corners with four equivalent O(1)Y2Fe2 trigonal pyramids,  an edgeedge with one O(3)Y2MnFe tetrahedra,  an edgeedge with one O(1)Y2Fe2 trigonal pyramid, and edges with two equivalent O(4)Y2Mn2 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Mn(1) atoms to form distorted OY2Mn2 trigonal pyramids that share corners with four equivalent O(3)Y2MnFe tetrahedra, corners with two equivalent O(4)Y2Mn2 trigonal pyramids, corners with four equivalent O(1)Y2Fe2 trigonal pyramids, edges with four equivalent O(3)Y2MnFe tetrahedra, and  an edgeedge with one O(4)Y2Mn2 trigonal pyramid.