Figure 2: Magnetoresistance and magnetic torque of CeRhIn₅ at 380 mK.

Resistivity along the a- and the c-direction, as well as (b) the magnetic torque of CeRhIn₅ single crystals in fields tilted 20° away from the c axis at 380 mK. The two main observations of this study become evident: a hysteretic, first-order-like transition in field occurring at ~30 T, which is marked by a salient jump in the in-plane resistivity. Remarkably, the out-of-plane resistivity, as well as the magnetic torque, remain featureless across the transition. The inset shows the torque on an amplified scale around the region of the resistive anomaly, with fields of the up- and downward resistivity jumps indicated by arrows and a linear fit to the data (red). Except for de Haas–van Alphen oscillations, the torque remains featureless in this region. This suggests a change in two-dimensional pieces of the Fermi surface prominent in the in-plane transport, but which do not contribute significantly to the out-of-plane transport. At the same time, the featureless torque indicates that a very subtle and practically imperceptible change in the magnetic susceptibility between the two states.