DUALITY OF LOCALISED AND DE-LOCALIZED CHARACTERS OF 4F ELECTRONS IN CERIUM COMPOUNDS

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The intermetallic compound CePdAl is a typical example to study intermediate characters between localization and de-localization of 4felectrons in the cerium compound. However, there was not good sample with a residual resistibility less than a few mΩcm when the experiments started on this samples. We have focused on this sample and concentrated ourselves to grow good single-crystalline samples. We have succeeded to prepare a single crystal with 20μΩcm, and it drops a few μΩcm under magnetic fields, suggesting a possibility to detect the de Haas-van Alphen oscillations. Main results obtained here are as follows:1. Single crystalline samples of C (Pd_<1-x>Ni_x)Al have been successfully prepared, where x ranges from 0.0 to 1.0.2. The electrical resistibility, magnetic susceptibility, and specific heat experiments have been carried out under the extreme conditions, the lowest temperature 0.1K, the maximum pressure 1.3 GPa and the highest field 15 T. From these experimental results, it is found that (1) the Neel temperature smoothly decreases and disappears as the pressure increases, (2) at the same time the magnetization of 4f electrons diminishes. These results are consistent with those of the instituted systems of Ce(Pd_<1-x>Ni_x)Al.3. The temperature dependence of the electrical resistibility shows non-Fermi liquid behaviors as T^<1.5> down to 0.1K. But this character collapses under the magnetic field 7T, and a Fermi liquid behavior revives, i.e., ρ〜T^2.4. The thermoelectric power of single crystalline samples of Ce(Pd_<1-x>Ni_x)Al shows huge positive value around 100 K in x 〜 0.4 far different from the critical concentration x_e 〜 0.1, and the initial slope dS/dT at low temperatures also makes a maximum at x 〜 0.4.