YbAlB4 is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Pmmm space group. Yb(1) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form YbB12 cuboctahedra that share edges with four equivalent Yb(1)B12 cuboctahedra, edges with eight equivalent Al(1)B12 cuboctahedra, faces with four equivalent Yb(1)B12 cuboctahedra, and faces with four equivalent Al(1)B12 cuboctahedra. Al(1) is bonded to four equivalent B(1) and eight equivalent B(2) atoms to form AlB12 cuboctahedra that share edges with four equivalent Al(1)B12 cuboctahedra, edges with eight equivalent Yb(1)B12 cuboctahedra, faces with four equivalent Yb(1)B12 cuboctahedra, and faces with four equivalent Al(1)B12 cuboctahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to four equivalent Yb(1), two equivalent Al(1), one B(1), and two equivalent B(2) atoms. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Yb(1), four equivalent Al(1), one B(2), and two equivalent B(1) atoms.
YbAlB4 is hexagonal omega structure-derived structured and crystallizes in the orthorhombic Pmmm space group. Yb(1) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form YbB12 cuboctahedra that share edges with four equivalent Yb(1)B12 cuboctahedra, edges with eight equivalent Al(1)B12 cuboctahedra, faces with four equivalent Yb(1)B12 cuboctahedra, and faces with four equivalent Al(1)B12 cuboctahedra. All Yb(1)-B(2) bond lengths are 2.57 Å. All Yb(1)-B(1) bond lengths are 2.58 Å. Al(1) is bonded to four equivalent B(1) and eight equivalent B(2) atoms to form AlB12 cuboctahedra that share edges with four equivalent Al(1)B12 cuboctahedra, edges with eight equivalent Yb(1)B12 cuboctahedra, faces with four equivalent Yb(1)B12 cuboctahedra, and faces with four equivalent Al(1)B12 cuboctahedra. All Al(1)-B(1) bond lengths are 2.48 Å. All Al(1)-B(2) bond lengths are 2.54 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to four equivalent Yb(1), two equivalent Al(1), one B(1), and two equivalent B(2) atoms. The B(1)-B(1) bond length is 1.97 Å. Both B(1)-B(2) bond lengths are 1.79 Å. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Yb(1), four equivalent Al(1), one B(2), and two equivalent B(1) atoms. The B(2)-B(2) bond length is 1.71 Å.