Anomalous Field and Temperature Dependence of the dHvA Oscillations in PrPb3

We have performed wave form analysis of the dHvA oscillations in PrPb 3 to investigate the interaction between conduction electrons and quadrupoles. It is found that each dHvA oscillation consists of two component oscillations which most likely originate from the up and down spin bands, and the effective masses of the two component oscillations differ from each other by about a factor of two or more, although the frequencies are close to each other. Analysis of the γ oscillation indicates that the effective mass is enhanced near the phase boundary between para- and antiferro-quadrupolar phases and decreases with increasing field at higher magnetic fields.