Cr3AlB4 crystallizes in the orthorhombic Pmmm space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 6-coordinate geometry to two equivalent B(1) and four equivalent B(2) atoms. In the second Cr site, Cr(2) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form a mixture of edge and face-sharing CrB12 cuboctahedra. Al(1) is bonded in a distorted linear geometry to two equivalent B(2) atoms. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Cr(1), four equivalent Cr(2), 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 Cr(2), four equivalent Cr(1), one Al(1), and two equivalent B(1) atoms.
Cr3AlB4 crystallizes in the orthorhombic Pmmm space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 6-coordinate geometry to two equivalent B(1) and four equivalent B(2) atoms. Both Cr(1)-B(1) bond lengths are 2.12 Å. All Cr(1)-B(2) bond lengths are 2.15 Å. In the second Cr site, Cr(2) is bonded to four equivalent B(2) and eight equivalent B(1) atoms to form a mixture of edge and face-sharing CrB12 cuboctahedra. All Cr(2)-B(2) bond lengths are 2.32 Å. All Cr(2)-B(1) bond lengths are 2.24 Å. Al(1) is bonded in a distorted linear geometry to two equivalent B(2) atoms. Both Al(1)-B(2) bond lengths are 2.23 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to two equivalent Cr(1), four equivalent Cr(2), one B(1), and two equivalent B(2) atoms. The B(1)-B(1) bond length is 1.74 Å. Both B(1)-B(2) bond lengths are 1.73 Å. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Cr(2), four equivalent Cr(1), one Al(1), and two equivalent B(1) atoms.