The question addressed here is whether there is structure in the narrow renormalized quasiparticle bands due to coherence in a periodic heavy fermion lattice. In CeCu6 the specific heat indicates that the Fermi temperature, TF, is about 3 K. We find that for a crystal of CeCu6, well below TF, the Hall constant shows changes in behavior at about 400 mK and again at 25 mK. This result is evidence that there is structure in the band on a scale smaller than TF due to the periodicity of the Kondo lattice system. © 1988.

The Hall effect is found to set the scale for coherence in the normal state of CeCu6 and U2PtC2. CeCu6 is a nonmagnetic, nonsuperconducting heavy fermion system.1–4 Its resistivity at high temperature is like that of a collection of incoherent Kondo scatterers. At low temperature the resistivity smoothly decreases to a very small value, indicating that scattering has become coherent. The Hall effect has two strong extrema in its temperature dependence which define a high-temperature incoherent scattering region, a transition region, and a low temperature coherent region. Although U2PtC2 is superconducting below 1.5 K,5 the Hall results in the normal state show two extrema similar to those of CeCu6. However, these features are scaled to higher temperatures, consistent with the smaller low-temperature electronic specific heat and higher Fermi temperature.

The Hall effect in both UBe13 and CeCu6 becomes very large at low temperature showing, with the resistivity and specific heat, the transition into the heavy fermion state. The Hall constant of CeCu6 changes sign, on cooling into the coherently scattering regime. © 1986.

The onset of heavy-fermion coherent-ground-state behavior is studied in CeCu6 by Hall-effect and magnetoresistance measurements. CeCu6 is an ideal system for this study since the fermions are extremely heavy and the system does not become either magnetic or superconducting. The strong temperature dependence of the Hall effect sets the scale for the high-temperature, single-Kondo-impurity, incoherent regime, a broad transition region, and the very-low-temperature coherent regime. In contrast to the resistivity, which shows a gradual transition to the coherent state, the Hall effect shows a rather sharp feature at the onset of coherence. © 1986 The American Physical Society.