MAGNETORESISTANCE AND DEHAAS-VANALPHEN EFFECT IN CERU2SI2 AND LARU2SI2

We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in CeRu2Si2 and LaRu2Si2. From the results of magnetoresistance, CeRu2Si2 is concluded to be a compensated metal, possibly possessing an open orbit along the c-axis of the tetragonal structure. On the other hand, LaRu2Si2 is an uncompensated metal, showing the saturated magnetoresistance. These results imply that the 4f electrons in CeRu2Si2 are itinerant. In the dHvA experiments of LaRu2Si2, we have found a large ellipsoidal Fermi surface which occupies roughly half of the Brillouin zone in volume. On the other hand, CeRu2Si2 possesses multiply connected Fermi surfaces in part, although main Fermi surfaces are not observed yet.