We present quantum oscillations observed in the heavy-fermion compound YbPtBi in magnetic fields far beyond its field-tuned, quantum critical point. Quantum oscillations are observed in magnetic fields as low as 60 kOe at 60 mK and up to temperatures as high as 3 K, which confirms the very high quality of the samples as well as the small effective mass of the conduction carriers far from the quantum critical point. Although the electronic specific heat coefficient of YbPtBi reaches $\sim 7.4\mathrm{J}/\mathrm{mol}{\mathrm{K}}^2$ in zero field, which is one of the highest effective mass values among heavy-fermion systems, it is suppressed quickly by an applied magnetic field. The quantum oscillations were used to extract the quasiparticle effective masses of the order of the bare electron mass, which is consistent with the behavior observed in specific heat measurements. Such small effective masses at high fields can be understood by considering the suppression of Kondo screening.

• Received 29 June 2015

DOI:https://doi.org/10.1103/PhysRevB.92.085135