U3HfSb5 crystallizes in the monoclinic C2/m space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 9-coordinate geometry to one Sb(4), two equivalent Sb(1), two equivalent Sb(2), and four equivalent Sb(3) atoms. In the second U site, U(2) is bonded in a 9-coordinate geometry to two equivalent Sb(1), two equivalent Sb(2), two equivalent Sb(3), and three equivalent Sb(4) atoms. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to two equivalent Sb(4) and four equivalent Sb(3) atoms to form face-sharing HfSb6 octahedra. In the second Hf site, Hf(2) is bonded to two equivalent Sb(4) and four equivalent Sb(3) atoms to form face-sharing HfSb6 octahedra. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 8-coordinate geometry to two equivalent U(2), four equivalent U(1), and two equivalent Sb(2) atoms. In the second Sb site, Sb(2) is bonded in a 8-coordinate geometry to two equivalent U(2), four equivalent U(1), and two equivalent Sb(1) atoms. In the third Sb site, Sb(3) is bonded to one U(2), four equivalent U(1), one Hf(1), and one Hf(2) atom to form a mixture of distorted face, corner, and edge-sharing SbHf2U5 pentagonal bipyramids. In the fourth Sb site, Sb(4) is bonded to two equivalent U(1), three equivalent U(2), one Hf(1), and one Hf(2) atom to form a mixture of distorted face, corner, and edge-sharing SbHf2U5 pentagonal bipyramids.
U3HfSb5 crystallizes in the monoclinic C2/m space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 9-coordinate geometry to one Sb(4), two equivalent Sb(1), two equivalent Sb(2), and four equivalent Sb(3) atoms. The U(1)-Sb(4) bond length is 3.19 Å. There is one shorter (3.28 Å) and one longer (3.29 Å) U(1)-Sb(1) bond length. There is one shorter (3.29 Å) and one longer (3.30 Å) U(1)-Sb(2) bond length. There are a spread of U(1)-Sb(3) bond distances ranging from 3.19-3.36 Å. In the second U site, U(2) is bonded in a 9-coordinate geometry to two equivalent Sb(1), two equivalent Sb(2), two equivalent Sb(3), and three equivalent Sb(4) atoms. Both U(2)-Sb(1) bond lengths are 3.29 Å. Both U(2)-Sb(2) bond lengths are 3.29 Å. Both U(2)-Sb(3) bond lengths are 3.19 Å. There are a spread of U(2)-Sb(4) bond distances ranging from 3.25-3.37 Å. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to two equivalent Sb(4) and four equivalent Sb(3) atoms to form face-sharing HfSb6 octahedra. Both Hf(1)-Sb(4) bond lengths are 2.93 Å. All Hf(1)-Sb(3) bond lengths are 2.93 Å. In the second Hf site, Hf(2) is bonded to two equivalent Sb(4) and four equivalent Sb(3) atoms to form face-sharing HfSb6 octahedra. Both Hf(2)-Sb(4) bond lengths are 2.93 Å. All Hf(2)-Sb(3) bond lengths are 2.93 Å. There are four inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 8-coordinate geometry to two equivalent U(2), four equivalent U(1), and two equivalent Sb(2) atoms. Both Sb(1)-Sb(2) bond lengths are 3.13 Å. In the second Sb site, Sb(2) is bonded in a 8-coordinate geometry to two equivalent U(2), four equivalent U(1), and two equivalent Sb(1) atoms. In the third Sb site, Sb(3) is bonded to one U(2), four equivalent U(1), one Hf(1), and one Hf(2) atom to form a mixture of distorted face, corner, and edge-sharing SbHf2U5 pentagonal bipyramids. In the fourth Sb site, Sb(4) is bonded to two equivalent U(1), three equivalent U(2), one Hf(1), and one Hf(2) atom to form a mixture of distorted face, corner, and edge-sharing SbHf2U5 pentagonal bipyramids.