Instability Of The F-Electron State In Uru2si2-Xpx Probed Using High Magnetic Fields

The widely studied hidden-order phase in URu2Si2 exemplifies a broad class of emergent macroscopic states originating from d- and f-electron orbitals and their collective modes. This naturally has resulted in a focus on the associated elements (i.e., U and Ru), but recently it was discovered that electronic tuning on the more passive s and p orbitals fundamentally alters the electronic behavior and thus opens opportunities to disentangle the hidden-order conundrum. Here we present a detailed magnetoresistivity study of URu2Si2-xPx, which focuses on two important aspects of this topic. First, we show that the anisotropy of the high field ordered states is preserved after hidden order is destroyed by Si -> P chemical substitution, suggesting that this feature is mainly associated with the Kondo lattice, i.e., not hidden order itself. Second, Shubnikov-de Haas oscillations reveal that the observable parts of the Fermi surface topography are robust upon approaching the hidden-order phase boundary and the associated quasiparticle masses remain roughly constant. These observations place constraints on theories and prepare a path towards a resolution to the hidden-order problem.