Intermetallic compounds Ce4Ru3Ga3 and La3Ru2Ga2 with crystal structures of new types

Highlights: •Novel intermetallic phases Ce4Ru3Ga3 and La3Ru2Ga2 with new structural types. •Unusual short Ce–Ru contact of 2.7167 Å in Ce4Ru3Ga3. •The average valence of cerium in intermetallic Ce4Ru3Ga3 is higher than three. •The Ce4Ru3Ga3 compound exhibits metallic conductivity. •Cerium atom adopts an intermediate valence state. -- Abstract: Novel intermetallic phases Ce4Ru3Ga3 and La3Ru2Ga2 were synthesized by arc melting the elemental components. The Ce4Ru3Ga3 compound crystallizes with the orthorhombic unit cell of new structural type (space group Pnna, Z = 4) and the lattice parameters: a = 7.719(4) Å, b = 18.578(12) Å, c = 5.673(3) Å; while the La3Ru2Ga2 compound has the monoclinic unit cell of new type (space group P21/m, Z = 6) and the lattice parameters: a = 5.8170(15) Å, b = 13.980(3) Å, c = 12.224(3) Å, β = 97.958(6)°. The characteristic feature of the Ce4Ru3Ga3 structure is very short distance of 2.7167 Å between one of the ruthenium atoms and one of the cerium atoms. This cerium atom adopts the intermediate valence state, which is reflected in the characteristic temperature dependence of the magnetic susceptibility of Ce4Ru3Ga3 and was directly confirmed by XANES spectroscopy. The latter experiment yielded the average valence of cerium ions near room temperature to be 3.19 ± 0.01. The compound exhibits metallic conductivity, fully consistent with its intermediate valence character