Anomalous f-electron Hall effect in the heavy-electron alloy Ce$_{1-x}$La$_{x}$CoIn$_{5}$

We report the results of Hall effect measurements made on the heavy-electron alloy Ce$_{1-x}$La$_{x}$CoIn$_{5}$ in magnetic fields from 1 to 90 kOe and at temperatures from 2 to 300 K. $R_{H}(T)$ of CeCoIn$_{5}$ is negative, field-independent, and dominated by skew-scattering above $\sim$ 50 K. $R_{H}(H \rightarrow 0)$ becomes increasingly negative below 50 K and varies with temperature in a manner that is inconsistent with skew scattering. Field-dependent measurements show that the low-T anomaly is strongly suppressed when the applied field is increased to 90 kOe. Measurements on LaCoIn$_{5}$ indicate that the same anomalous temperature dependence is present in the Hall coefficient of this non-magnetic analog, albeit with a reduced amplitude and no field dependence. By measuring $R_{H}(T,H)$ in Ce$_{1-x}$La$_{x}$CoIn$_{5}$ alloys we can discriminate between the influence of many-body Kondo interactions and conventional band-structure effects on the Hall coefficient in the parent compound. The results are generally consistent with a two-fluid description of Kondo lattice systems proposed by Nakatsuji \textit{et al.}.\footnote{S. Nakatsuji \textit{et al.}, Phys. Rev. Lett. \textbf{92}, 016401 (2004)}