THERMAL-EXPANSION AND COMPRESSIBILITY OF SR2RUO4

The thermal expansion and compressibility of Sr2RuO4 have been investi gated using neutron-powder diffraction. Our results confirm that the t emperature dependence of the Ru-O2 apical bond length is linear with n o structural anomaly (reported previously) corresponding to the metal- to-insulator transition. The response of the crystal lattice of Sr2RuO 4 to pressure is similar to that of the superconducting cuprate (La,Sr )(2)CuO4. However, the Ru-O2 apical bond is much harder to compress th an the corresponding Cu-O2 bond.