CeRh₂Al₁₀ – The first rhodium aluminide with a new structure type in the 1:2:10 stoichiometry family

A new member of the RET₂Al₁₀ family was synthesized and its crystal structure was determined from single crystal X-ray diffraction. The first aluminide with rhodium adopts a new structure type of 1:2:10 stoichiometry. CeRh₂Al₁₀ crystallizes in the tetragonal space group I4₁/amd with cell parameters a = 8.9284(11) Å and c = 21.769(3) Å and is a substitution variant of CePd₃Al₉ compound. The mutual arrangement of Rh and Al neighbors within the 20-vertex Ce polyhedron differs in comparison with that of the CeRu₂Al₁₀ structure. This leads to the different packing of Ce polyhedra in the unit cell. In CeRh₂Al₁₀, zig-zag chains of the shortest Ce–Ce contacts extend in the two mutually perpendicular directions – along the a-axis and along the b-axis. In contrast, in CeRu₂Al₁₀, zig-zag chains of the shortest Ce–Ce contacts run in one direction – along the c-axis. We illustrate using key physical properties how the variation in crystal structure produces physical properties in CeRh₂Al₁₀ that differ strikingly from the situation in CeRu₂Al₁₀.