U5Rh15B4 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Rh(1), four equivalent Rh(4), and four equivalent Rh(5) atoms to form URh12 cuboctahedra that share corners with four equivalent U(2)Rh12 cuboctahedra, corners with eight equivalent U(1)Rh12 cuboctahedra,  a faceface with one U(2)Rh12 cuboctahedra, faces with five equivalent U(1)Rh12 cuboctahedra, and faces with four equivalent B(1)Rh6 octahedra. In the second U site, U(2) is bonded to four equivalent Rh(2), four equivalent Rh(5), and four equivalent Rh(6) atoms to form URh12 cuboctahedra that share corners with four equivalent U(1)Rh12 cuboctahedra, corners with four equivalent U(2)Rh12 cuboctahedra, corners with four equivalent U(3)Rh12 cuboctahedra,  a faceface with one U(1)Rh12 cuboctahedra,  a faceface with one U(3)Rh12 cuboctahedra, faces with four equivalent U(2)Rh12 cuboctahedra, faces with four equivalent B(1)Rh6 octahedra, and faces with four equivalent B(2)Rh6 octahedra. In the third U site, U(3) is bonded to four equivalent Rh(3) and eight equivalent Rh(6) atoms to form URh12 cuboctahedra that share corners with four equivalent U(3)Rh12 cuboctahedra, corners with eight equivalent U(2)Rh12 cuboctahedra, faces with two equivalent U(2)Rh12 cuboctahedra, faces with four equivalent U(3)Rh12 cuboctahedra, and faces with eight equivalent B(2)Rh6 octahedra. There are six inequivalent Rh sites. In the first Rh site, Rh(1) is bonded in a distorted single-bond geometry to four equivalent U(1) and one B(1) atom. In the second Rh site, Rh(2) is bonded to four equivalent U(2), one B(1), and one B(2) atom to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the third Rh site, Rh(3) is bonded to four equivalent U(3) and two equivalent B(2) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the fourth Rh site, Rh(4) is bonded in a distorted square co-planar geometry to four equivalent U(1) atoms. In the fifth Rh site, Rh(5) is bonded to two equivalent U(1), two equivalent U(2), and two equivalent B(1) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the sixth Rh site, Rh(6) is bonded to two equivalent U(2), two equivalent U(3), and two equivalent B(2) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. There are two inequivalent B sites. In the first B site, B(1) is bonded to one Rh(1), one Rh(2), and four equivalent Rh(5) atoms to form BRh6 octahedra that share  a cornercorner with one B(2)Rh6 octahedra, corners with four equivalent B(1)Rh6 octahedra, faces with four equivalent U(1)Rh12 cuboctahedra, and faces with four equivalent U(2)Rh12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second B site, B(2) is bonded to one Rh(2), one Rh(3), and four equivalent Rh(6) atoms to form BRh6 octahedra that share  a cornercorner with one B(1)Rh6 octahedra, corners with five equivalent B(2)Rh6 octahedra, faces with four equivalent U(2)Rh12 cuboctahedra, and faces with four equivalent U(3)Rh12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-2°.
U5Rh15B4 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Rh(1), four equivalent Rh(4), and four equivalent Rh(5) atoms to form URh12 cuboctahedra that share corners with four equivalent U(2)Rh12 cuboctahedra, corners with eight equivalent U(1)Rh12 cuboctahedra,  a faceface with one U(2)Rh12 cuboctahedra, faces with five equivalent U(1)Rh12 cuboctahedra, and faces with four equivalent B(1)Rh6 octahedra. All U(1)-Rh(1) bond lengths are 2.98 Å. All U(1)-Rh(4) bond lengths are 2.85 Å. All U(1)-Rh(5) bond lengths are 3.02 Å. In the second U site, U(2) is bonded to four equivalent Rh(2), four equivalent Rh(5), and four equivalent Rh(6) atoms to form URh12 cuboctahedra that share corners with four equivalent U(1)Rh12 cuboctahedra, corners with four equivalent U(2)Rh12 cuboctahedra, corners with four equivalent U(3)Rh12 cuboctahedra,  a faceface with one U(1)Rh12 cuboctahedra,  a faceface with one U(3)Rh12 cuboctahedra, faces with four equivalent U(2)Rh12 cuboctahedra, faces with four equivalent B(1)Rh6 octahedra, and faces with four equivalent B(2)Rh6 octahedra. All U(2)-Rh(2) bond lengths are 2.98 Å. All U(2)-Rh(5) bond lengths are 2.96 Å. All U(2)-Rh(6) bond lengths are 3.00 Å. In the third U site, U(3) is bonded to four equivalent Rh(3) and eight equivalent Rh(6) atoms to form URh12 cuboctahedra that share corners with four equivalent U(3)Rh12 cuboctahedra, corners with eight equivalent U(2)Rh12 cuboctahedra, faces with two equivalent U(2)Rh12 cuboctahedra, faces with four equivalent U(3)Rh12 cuboctahedra, and faces with eight equivalent B(2)Rh6 octahedra. All U(3)-Rh(3) bond lengths are 2.98 Å. All U(3)-Rh(6) bond lengths are 2.98 Å. There are six inequivalent Rh sites. In the first Rh site, Rh(1) is bonded in a distorted single-bond geometry to four equivalent U(1) and one B(1) atom. The Rh(1)-B(1) bond length is 2.00 Å. In the second Rh site, Rh(2) is bonded to four equivalent U(2), one B(1), and one B(2) atom to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. The Rh(2)-B(1) bond length is 2.22 Å. The Rh(2)-B(2) bond length is 2.11 Å. In the third Rh site, Rh(3) is bonded to four equivalent U(3) and two equivalent B(2) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. Both Rh(3)-B(2) bond lengths are 2.15 Å. In the fourth Rh site, Rh(4) is bonded in a distorted square co-planar geometry to four equivalent U(1) atoms. In the fifth Rh site, Rh(5) is bonded to two equivalent U(1), two equivalent U(2), and two equivalent B(1) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. Both Rh(5)-B(1) bond lengths are 2.11 Å. In the sixth Rh site, Rh(6) is bonded to two equivalent U(2), two equivalent U(3), and two equivalent B(2) atoms to form a mixture of distorted corner, edge, and face-sharing RhU4B2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. Both Rh(6)-B(2) bond lengths are 2.11 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded to one Rh(1), one Rh(2), and four equivalent Rh(5) atoms to form BRh6 octahedra that share  a cornercorner with one B(2)Rh6 octahedra, corners with four equivalent B(1)Rh6 octahedra, faces with four equivalent U(1)Rh12 cuboctahedra, and faces with four equivalent U(2)Rh12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second B site, B(2) is bonded to one Rh(2), one Rh(3), and four equivalent Rh(6) atoms to form BRh6 octahedra that share  a cornercorner with one B(1)Rh6 octahedra, corners with five equivalent B(2)Rh6 octahedra, faces with four equivalent U(2)Rh12 cuboctahedra, and faces with four equivalent U(3)Rh12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-2°.