Evidence for unconventional superconductivity of Sr2RuO4 from specific-heat measurements

We measured the specific heat of single crystals of non-cuprate layered perovskite superconductor Sr2RuO4. The crystals with different T-c up to 1.2 K exhibit a large residual electronic coefficient gamma omicron, which decreases systematically with increasing T-c. This behavior is consistent with the presence of nodes in the superconducting gap and with the variations of T-c due to pair breaking by impurities and defects. To quantitatively account for the observed large gamma omicron, however, we need to introduce additional mechanism.