YGaMnO5 crystallizes in the orthorhombic Pbam space group. Y(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Mn(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Ga(1)O5 square pyramids and edges with two equivalent Mn(1)O6 octahedra. Ga(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted GaO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  an edgeedge with one Ga(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-54°. There are four inequivalent O sites. In the first O site, O(1) 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)Y2MnGa tetrahedra, corners with two equivalent O(1)Y2Mn2 trigonal pyramids, corners with four equivalent O(2)Y2Ga2 trigonal pyramids, edges with four equivalent O(3)Y2MnGa tetrahedra, and  an edgeedge with one O(1)Y2Mn2 trigonal pyramid. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Ga(1) atoms to form distorted OY2Ga2 trigonal pyramids that share corners with eight equivalent O(3)Y2MnGa tetrahedra, corners with four equivalent O(1)Y2Mn2 trigonal pyramids, edges with two equivalent O(3)Y2MnGa tetrahedra, and edges with two equivalent O(2)Y2Ga2 trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Y(1), one Mn(1), and one Ga(1) atom to form distorted OY2MnGa tetrahedra that share corners with six equivalent O(3)Y2MnGa tetrahedra, corners with two equivalent O(1)Y2Mn2 trigonal pyramids, corners with four equivalent O(2)Y2Ga2 trigonal pyramids,  an edgeedge with one O(3)Y2MnGa tetrahedra,  an edgeedge with one O(2)Y2Ga2 trigonal pyramid, and edges with two equivalent O(1)Y2Mn2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one Ga(1) atom.
YGaMnO5 crystallizes in the orthorhombic Pbam space group. Y(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. There is one shorter (2.33 Å) and one longer (2.43 Å) Y(1)-O(1) bond length. Both Y(1)-O(2) bond lengths are 2.32 Å. There are two shorter (2.36 Å) and two longer (2.47 Å) Y(1)-O(3) bond lengths. Mn(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Ga(1)O5 square pyramids and edges with two equivalent Mn(1)O6 octahedra. Both Mn(1)-O(1) bond lengths are 1.90 Å. Both Mn(1)-O(3) bond lengths are 1.90 Å. Both Mn(1)-O(4) bond lengths are 1.88 Å. Ga(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted GaO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  an edgeedge with one Ga(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-54°. The Ga(1)-O(4) bond length is 1.87 Å. Both Ga(1)-O(2) bond lengths are 1.96 Å. Both Ga(1)-O(3) bond lengths are 1.93 Å. There are four inequivalent O sites. In the first O site, O(1) 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)Y2MnGa tetrahedra, corners with two equivalent O(1)Y2Mn2 trigonal pyramids, corners with four equivalent O(2)Y2Ga2 trigonal pyramids, edges with four equivalent O(3)Y2MnGa tetrahedra, and  an edgeedge with one O(1)Y2Mn2 trigonal pyramid. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Ga(1) atoms to form distorted OY2Ga2 trigonal pyramids that share corners with eight equivalent O(3)Y2MnGa tetrahedra, corners with four equivalent O(1)Y2Mn2 trigonal pyramids, edges with two equivalent O(3)Y2MnGa tetrahedra, and edges with two equivalent O(2)Y2Ga2 trigonal pyramids. In the third O site, O(3) is bonded to two equivalent Y(1), one Mn(1), and one Ga(1) atom to form distorted OY2MnGa tetrahedra that share corners with six equivalent O(3)Y2MnGa tetrahedra, corners with two equivalent O(1)Y2Mn2 trigonal pyramids, corners with four equivalent O(2)Y2Ga2 trigonal pyramids,  an edgeedge with one O(3)Y2MnGa tetrahedra,  an edgeedge with one O(2)Y2Ga2 trigonal pyramid, and edges with two equivalent O(1)Y2Mn2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one Ga(1) atom.