U2FeS5 crystallizes in the monoclinic C2/c space group. U(1) is bonded in a 8-coordinate geometry to two equivalent S(3), three equivalent S(1), and three equivalent S(2) atoms. Fe(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 39°. There are three inequivalent S sites. In the first S site, S(1) is bonded to three equivalent U(1) and two equivalent Fe(1) atoms to form distorted SU3Fe2 trigonal bipyramids that share corners with two equivalent S(1)U3Fe2 trigonal bipyramids, corners with four equivalent S(3)U4 trigonal pyramids, edges with five equivalent S(1)U3Fe2 trigonal bipyramids, and  an edgeedge with one S(3)U4 trigonal pyramid. In the second S site, S(2) is bonded in a 4-coordinate geometry to three equivalent U(1) and one Fe(1) atom. In the third S site, S(3) is bonded to four equivalent U(1) atoms to form SU4 trigonal pyramids that share corners with eight equivalent S(1)U3Fe2 trigonal bipyramids, edges with two equivalent S(1)U3Fe2 trigonal bipyramids, and edges with two equivalent S(3)U4 trigonal pyramids.
U2FeS5 crystallizes in the monoclinic C2/c space group. U(1) is bonded in a 8-coordinate geometry to two equivalent S(3), three equivalent S(1), and three equivalent S(2) atoms. There is one shorter (2.72 Å) and one longer (2.75 Å) U(1)-S(3) bond length. There are a spread of U(1)-S(1) bond distances ranging from 2.73-2.77 Å. There are a spread of U(1)-S(2) bond distances ranging from 2.63-3.11 Å. Fe(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 39°. Both Fe(1)-S(2) bond lengths are 2.41 Å. There are two shorter (2.42 Å) and two longer (2.44 Å) Fe(1)-S(1) bond lengths. There are three inequivalent S sites. In the first S site, S(1) is bonded to three equivalent U(1) and two equivalent Fe(1) atoms to form distorted SU3Fe2 trigonal bipyramids that share corners with two equivalent S(1)U3Fe2 trigonal bipyramids, corners with four equivalent S(3)U4 trigonal pyramids, edges with five equivalent S(1)U3Fe2 trigonal bipyramids, and  an edgeedge with one S(3)U4 trigonal pyramid. In the second S site, S(2) is bonded in a 4-coordinate geometry to three equivalent U(1) and one Fe(1) atom. In the third S site, S(3) is bonded to four equivalent U(1) atoms to form SU4 trigonal pyramids that share corners with eight equivalent S(1)U3Fe2 trigonal bipyramids, edges with two equivalent S(1)U3Fe2 trigonal bipyramids, and edges with two equivalent S(3)U4 trigonal pyramids.