ErAlB14 is Magnesium tetraboride-derived structured and crystallizes in the orthorhombic Imma space group. Er(1) is bonded in a 16-coordinate geometry to two equivalent B(1), two equivalent B(2), four equivalent B(5), and eight equivalent B(4) atoms. Al(1) is bonded to four equivalent B(2), four equivalent B(3), and four equivalent B(5) atoms to form distorted face-sharing AlB12 cuboctahedra. There are five inequivalent B sites. In the first B site, B(1) is bonded in a 7-coordinate geometry to one Er(1), one B(1), one B(3), two equivalent B(4), and two equivalent B(5) atoms. In the second B site, B(2) is bonded in a 7-coordinate geometry to one Er(1), two equivalent Al(1), one B(2), one B(3), and two equivalent B(5) atoms. In the third B site, B(3) is bonded in a 8-coordinate geometry to two equivalent Al(1), one B(1), one B(2), two equivalent B(4), and two equivalent B(5) atoms. In the fourth B site, B(4) is bonded in a 8-coordinate geometry to two equivalent Er(1), one B(1), one B(3), two equivalent B(4), and two equivalent B(5) atoms. In the fifth B site, B(5) is bonded in a 8-coordinate geometry to one Er(1), one Al(1), one B(1), one B(2), one B(3), one B(5), and two equivalent B(4) atoms.
ErAlB14 is Magnesium tetraboride-derived structured and crystallizes in the orthorhombic Imma space group. Er(1) is bonded in a 16-coordinate geometry to two equivalent B(1), two equivalent B(2), four equivalent B(5), and eight equivalent B(4) atoms. Both Er(1)-B(1) bond lengths are 2.72 Å. Both Er(1)-B(2) bond lengths are 2.54 Å. All Er(1)-B(5) bond lengths are 2.85 Å. There are four shorter (2.67 Å) and four longer (2.81 Å) Er(1)-B(4) bond lengths. Al(1) is bonded to four equivalent B(2), four equivalent B(3), and four equivalent B(5) atoms to form distorted face-sharing AlB12 cuboctahedra. All Al(1)-B(2) bond lengths are 2.11 Å. All Al(1)-B(3) bond lengths are 2.33 Å. All Al(1)-B(5) bond lengths are 2.43 Å. There are five inequivalent B sites. In the first B site, B(1) is bonded in a 7-coordinate geometry to one Er(1), one B(1), one B(3), two equivalent B(4), and two equivalent B(5) atoms. The B(1)-B(1) bond length is 1.73 Å. The B(1)-B(3) bond length is 1.84 Å. Both B(1)-B(4) bond lengths are 1.81 Å. Both B(1)-B(5) bond lengths are 1.85 Å. In the second B site, B(2) is bonded in a 7-coordinate geometry to one Er(1), two equivalent Al(1), one B(2), one B(3), and two equivalent B(5) atoms. The B(2)-B(2) bond length is 2.21 Å. The B(2)-B(3) bond length is 1.80 Å. Both B(2)-B(5) bond lengths are 1.75 Å. In the third B site, B(3) is bonded in a 8-coordinate geometry to two equivalent Al(1), one B(1), one B(2), two equivalent B(4), and two equivalent B(5) atoms. Both B(3)-B(4) bond lengths are 1.85 Å. Both B(3)-B(5) bond lengths are 1.76 Å. In the fourth B site, B(4) is bonded in a 8-coordinate geometry to two equivalent Er(1), one B(1), one B(3), two equivalent B(4), and two equivalent B(5) atoms. There is one shorter (1.78 Å) and one longer (1.92 Å) B(4)-B(4) bond length. Both B(4)-B(5) bond lengths are 1.82 Å. In the fifth B site, B(5) is bonded in a 8-coordinate geometry to one Er(1), one Al(1), one B(1), one B(2), one B(3), one B(5), and two equivalent B(4) atoms. The B(5)-B(5) bond length is 1.85 Å.