DOE OSTI2020
UMn3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded to twelve Mn atoms to form UMn12 cuboctahedra that share corners with four equivalent UMn12 cuboctahedra, corners with eight equivalent MnU4Mn8 cuboctahedra, edges with eight equivalent UMn12 cuboctahedra, edges with sixteen equivalent MnU4Mn8 cuboctahedra, faces with four equivalent UMn12 cuboctahedra, and faces with fourteen MnU4Mn8 cuboctahedra. There are eight shorter (2.67 Å) and four longer (2.69 Å) U–Mn bond lengths. There are two inequivalent Mn sites. In the first Mn site, Mn is bonded to four equivalent U and eight equivalent Mn atoms to form MnU4Mn8 cuboctahedra that share corners with four equivalent MnU4Mn8 cuboctahedra, corners with eight equivalent UMn12 cuboctahedra, edges with twenty-four MnU4Mn8 cuboctahedra, faces with six equivalent UMn12 cuboctahedra, and faces with twelve MnU4Mn8 cuboctahedra. All Mn–Mn bond lengths are 2.67 Å. In the second Mn site, Mn is bonded to four equivalent U and eight Mn atoms to form MnU4Mn8 cuboctahedra that share corners with twelve equivalent MnU4Mn8 cuboctahedra, edges with eight equivalent UMn12 cuboctahedra, edges with sixteen MnU4Mn8 cuboctahedra, faces with four equivalent UMn12 cuboctahedra, and faces with fourteen MnU4Mn8 cuboctahedra. All Mn–Mn bond lengths are 2.69 Å.