Magnetic field-tuned localization of the 5f-electrons in URu2Si2

We report Shubnikov-de Haas oscillation measurements within the high magnetic field (mu H-0 > 39 T) magnetically polarized regime of URu2Si2, made possible using mesoscopic samples prepared by means of focused ion beam lithography. A significant change in the Fermi surface topology relative to the hidden-order phase is observed, signaling a transformation into a high magnetic field regime in which 5f-electrons are removed from the Fermi surface. URu2Si2 is therefore a rare example of an actinide compound in which a transformation of 5f-electrons can be directly observed at low temperatures, setting the stage for the unconventional ordering and high magnetic field quantum criticality in this material.