ErReB4 crystallizes in the orthorhombic Pbam space group. Er(1) is bonded in a 18-coordinate geometry to four equivalent Re(1), two equivalent B(2), four equivalent B(1), four equivalent B(3), and four equivalent B(4) atoms. Re(1) is bonded in a 15-coordinate geometry to four equivalent Er(1), one Re(1), two equivalent B(1), two equivalent B(3), two equivalent B(4), and four equivalent B(2) atoms. There are four inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(2), and two equivalent B(4) atoms. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Er(1), four equivalent Re(1), one B(1), one B(2), and one B(3) atom. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(2), one B(3), and one B(4) atom. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(3), and two equivalent B(1) atoms.
ErReB4 crystallizes in the orthorhombic Pbam space group. Er(1) is bonded in a 18-coordinate geometry to four equivalent Re(1), two equivalent B(2), four equivalent B(1), four equivalent B(3), and four equivalent B(4) atoms. There are a spread of Er(1)-Re(1) bond distances ranging from 3.02-3.10 Å. Both Er(1)-B(2) bond lengths are 2.65 Å. There are two shorter (2.70 Å) and two longer (2.81 Å) Er(1)-B(1) bond lengths. All Er(1)-B(3) bond lengths are 2.75 Å. There are two shorter (2.73 Å) and two longer (2.79 Å) Er(1)-B(4) bond lengths. Re(1) is bonded in a 15-coordinate geometry to four equivalent Er(1), one Re(1), two equivalent B(1), two equivalent B(3), two equivalent B(4), and four equivalent B(2) atoms. The Re(1)-Re(1) bond length is 2.57 Å. Both Re(1)-B(1) bond lengths are 2.36 Å. Both Re(1)-B(3) bond lengths are 2.36 Å. Both Re(1)-B(4) bond lengths are 2.31 Å. There are two shorter (2.37 Å) and two longer (2.39 Å) Re(1)-B(2) bond lengths. There are four inequivalent B sites. In the first B site, B(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(2), and two equivalent B(4) atoms. The B(1)-B(2) bond length is 1.76 Å. There is one shorter (1.80 Å) and one longer (1.85 Å) B(1)-B(4) bond length. In the second B site, B(2) is bonded in a 9-coordinate geometry to two equivalent Er(1), four equivalent Re(1), one B(1), one B(2), and one B(3) atom. The B(2)-B(2) bond length is 1.74 Å. The B(2)-B(3) bond length is 1.75 Å. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(2), one B(3), and one B(4) atom. The B(3)-B(3) bond length is 1.76 Å. The B(3)-B(4) bond length is 1.82 Å. In the fourth B site, B(4) is bonded in a 9-coordinate geometry to four equivalent Er(1), two equivalent Re(1), one B(3), and two equivalent B(1) atoms.