Measurements of the temperature and concentration dependence of the specific heat, magnetic susceptibility, and electrical resistivity for Cei-x La^Pb3 are presented. The data scale with the concentration of Ce ions over surprisingly large intervals of x and T. The low-temperature specific heat per Ce ion agrees quantitatively with that of an S -j Kondo impurity of 7^ = 3.3 K. These results strongly suggest that intersite correlations do not play the expected important role and that the high specific heat y reported for CePl>3 is mainly a manifestation of the single-ion Kondo resonance. PACS numbers: 72.15.Qm, 75.20.Hr, 75.50.EeWithin condensed matter physics, one of the most exciting problems to have emerged during the last several years has been to understand the perplexing properties of heavy-fermion (HF) systems 1 " 3 and their relation to the broader issue of magnetic-moment formation. Characteristic of heavy fermions is an unusually large electronic specific heat at low temperatures, C -yT, where y corresponds to a very high density of states at the Fermi level or equivalently to an effective electron mass of 10 2 -10 3 times that of the free-electron mass. As a consequence of the large density of states these systems typically have a large Pauli susceptibility. The temperature dependence of C and X can be explained in terms of narrow resonant levels or a narrow band with a typical width of a few millielectronvolts or less. This narrow peak in the density of states has been attributed 2 ' 3 to a Kondo resonance, to hybridization effects and to Fermi-liquid properties, and its formation is still to be understood. Heavy-fermion behavior occurs in a variety of Ce-, Np-, U-, or Yb-based (concentrated or dilute) alloys and stoichiometric compounds.The low-temperature transport properties of stoichiometric HF compounds differ from those of alloys, while at high T, they are very similar. In compounds, the resistivity initially increases as one lowers T (which can be attributed to the Kondo effect), then goes through a large maximum and shows a sharp decrease at very low T. Both features, the existence of a maximum and the high resistivity at this maximum, are uncommon to normal metals. The rapid decrease of p(T) at low T is caused by a transition from incoherent to coherent scattering of the conduction electrons by the rare-earth (actinide) ions.

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