The dilute limit of heavy fermions: evidence of the coherent nature of CeAl(3).

Strongly diluted Ce(x)La(1-x)Al(3) alloys have been studied by the low temperature specific heat in order to elucidate the mechanism that determines their ground state. The results for alloys with Ce concentrations of 0.0005≤x≤0.1 are fairly consistent with a S = 1/2 Kondo behavior. However, the single-ion scaling is observed only below x = 0.01. The true single-ion Kondo temperature is small, 0.2 K, approximately equal to that for dilute CeAl(2). It is about 20 times smaller than that for CeAl(3), indicating the coherent nature of CeAl(3). The single-ion contribution to thermodynamic properties of CeAl(3) is negligible even at temperatures as high as 5 K.