UFe4B crystallizes in the hexagonal P6/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a distorted hexagonal planar geometry to six equivalent Fe(1) atoms. In the second U site, U(2) is bonded in a 18-coordinate geometry to twelve equivalent Fe(2) and six equivalent B(1) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent U(1), three equivalent Fe(1), and six equivalent Fe(2) atoms to form a mixture of distorted face, corner, and edge-sharing FeU3Fe9 cuboctahedra. In the second Fe site, Fe(2) is bonded in a distorted L-shaped geometry to two equivalent U(2), two equivalent Fe(1), and two equivalent B(1) atoms. B(1) is bonded in a 6-coordinate geometry to three equivalent U(2) and six equivalent Fe(2) atoms.
UFe4B crystallizes in the hexagonal P6/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a distorted hexagonal planar geometry to six equivalent Fe(1) atoms. All U(1)-Fe(1) bond lengths are 2.88 Å. In the second U site, U(2) is bonded in a 18-coordinate geometry to twelve equivalent Fe(2) and six equivalent B(1) atoms. All U(2)-Fe(2) bond lengths are 2.93 Å. All U(2)-B(1) bond lengths are 2.88 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent U(1), three equivalent Fe(1), and six equivalent Fe(2) atoms to form a mixture of distorted face, corner, and edge-sharing FeU3Fe9 cuboctahedra. All Fe(1)-Fe(1) bond lengths are 2.88 Å. All Fe(1)-Fe(2) bond lengths are 2.50 Å. In the second Fe site, Fe(2) is bonded in a distorted L-shaped geometry to two equivalent U(2), two equivalent Fe(1), and two equivalent B(1) atoms. Both Fe(2)-B(1) bond lengths are 2.10 Å. B(1) is bonded in a 6-coordinate geometry to three equivalent U(2) and six equivalent Fe(2) atoms.