Synthesis, crystal structure and physical properties of Ce2Ru2Ga3

The novel compound Ce2Ru2Ga3 was synthesized by arc-melting the elemental constituents in argon atmosphere followed by long-term annealing at 873 K. It forms in an orthorhombic system, with a crystal structure of new type (space group P212121, Z = 4, oP28) and the lattice parameters: a = 4.488(2) Å, b = 6.912(4) Å, c = 17.092(9) Å. The gallide is structurally related to intermetallics crystallizing with the NdRh2Sn4-type structure or its derivatives. It represents an unique family of materials with abnormally short Ce–Ru distances, which usually exhibit some instability of the valence state of cerium atoms. Based on the low-temperature magnetic and electrical transport data, as well as the X-ray absorption data, Ce2Ru2Ga3 has been characterised as another intermediate valence system.

► The gallide Ce2Ru2Ga3 crystallizes in a new structural type.
► Half of cerium atoms in Ce2Ru2Ga3 form very short Ce–Ru contacts.
► The average valence of cerium in Ce2Ru2Ga3 is higher than 3.
► Intermediate valence in Ce2Ru2Ga3 was proven by physical property measurements.