FIELD-INDUCED RENORMALIZATION OBSERVED BY MAGNETORESISTANCE IN CERU2SI2

We have measured the magnetoresistance of two CeRu2Si2 specimens issued from the same single crystal (with j parallel to the a-axis and parallel to the c-axis, respectively) at several fixed temperatures between 0.02 and 1.2 K in magnetic field up to 9 T applied paralrel to the c-axis. All rho vs. H curves show a maximum at the metamagnetic-like transition field B* = 7.7 T. When measured in constant applied field, the resistivity exhibits a quadratic temperature dependence (rho = rho(0)+AT(2)) at low temperature (< 0.3 K) in all cases, i.e. for B < B* as well as tor B > B*. The applied field brings about a larger change of the A term for j parallel to a than for j parallel to c, indicating that the field-induced mass renormalization occurs anisotropically in this compound. The magnitude of the mass enhancement given by the relation root A infinity gamma, is consistent with the previous enhancement derivPd from magnetization measurements via the Maxwell relation.