Metal-insulator transition in the amorphous CexSi100-x (4 <= x <= 83) heavy fermion system

The electronic structure, magnetic properties and electron transport proper ties have been studied on amorphous CexSi100-x (4 less than or equal to x l ess than or equal to 83) alloys in comparison with non-magnetic amorphous L axSi100-x (11 less than or equal to x less than or equal to 63) and TixSi10 0-x (6 less than or equal to x less than or equal to 41) alloys with a part icular emphasis on the formation of the pseudogap at the Fermi level and it s effect on the electron transport upon approaching the metal-insulator tra nsition in the heavy fermion system. It is shown that the interaction betwe en conduction electrons and localized moments leads to an anomalous enhance ment in the temperature dependence of the measured resistivity below 10 K. We also revealed that the amorphous CexSi100-x alloy system crosses the met al-insulator transition at about 12 at%Ce and that the marginally metallic Ce15Si85 alloy has the resistivity of 1500 mu Omega cm comparable to those in the non-magnetic reference systems but a large electronic specific heat coefficient gamma of 22 mJ/mol.K-2, which is 50 times as large as the value of 0.4 mJ/mol.K-2 for the marginally metallic Ti13Si87 alloy. The set of ( rho (300K), gamma (exp)) data fall on an extremely small diffusion constant line in the rho-gamma diagram. This unique behavior is attributed to the e xistence of Ce-4f electrons at the Fermi level, which give rise to a large value of gamma but are localized and immobile even in the metallic regime.