CeIrGaHy system: hydrogen induced structural and valence change

CeIrGa is shown to be a mixed-valent compound with very high Kondo temperature (≈1000 K). From the hydriding studies on CeIrGa, it is found that (i) only single hydride phase with hydrogen to metal ratio ≅1.7 is stabilized, which involves change of crystalline structure from orthorhombic (ε-TiNiSi type, space group Pnma) to hexagonal (B82 type, space group P63/mmc), and (ii) charge state of cerium changes from mixed-valent to Ce+3 state, though no magnetic ordering is observed down to 2 K.