Successive Electronic Topological Transitions in the Antiferromagnet UPd${}_2$Al${}_3$

Abstract

We report successive anomalies at low temperature in the magnetic field dependence of the thermoelectric signal in the heavy fermion compound UPd${}_2$Al${}_3$ inside the antiferromagnetic state up to the metamagnetic transition at $H_{\text{M}}=18$~T. Based on renormalisation perturbation theory and the partitioning of the $f$ orbitals into localized and delocalized parts, our analysis attributes these anomalies to complex topological changes of the Fermi surface driven by Zeeman effect. The observation of a sudden change of sign both in the thermoelectric power and in the Hall coefficient at $H_{\text{M}}$ in addition to the appearance of large quantum oscillations in the thermoelectric power above $H_{\text{M}}$ indicate a strong Fermi surface reconstruction at the metamagnetic transition due to the unfolding of the electronic bands.

14 pages, 12 figures