High magnetic fields induce a pronounced in-plane electronic anisotropy in the tetragonal antiferromagnetic metal CeRhIn5 at H∗30 T for fields ≃20° off the c axis. Here we investigate the response of the underlying crystal lattice in magnetic fields to 45 T via high-resolution dilatometry. At low fields, a finite magnetic field component in the tetragonal ab plane explicitly breaks the tetragonal (C4) symmetry of the lattice revealing a finite nematic susceptibility. A modest a-axis expansion at H∗ hence marks the crossover to a fluctuating nematic phase with large nematic susceptibility. Magnetostriction quantum oscillations confirm a Fermi surface change at H∗ with the emergence of new orbits. By analyzing the field-induced change in the crystal-field ground state, we conclude that the in-plane Ce 4f hybridization is enhanced at H∗, in agreement with the in-plane lattice expansion. We argue that the nematic behavior observed in this prototypical heavy-fermion material is of electronic origin, and is driven by the hybridization between 4f and conduction electrons which carries the f-electron anisotropy to the Fermi surface.
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We acknowledge constructive discussions with P. G. Pagliuso, R. R. Urbano, L. Jiao, A. Severing, M. Janoschek, and E. Miranda. P. F. S. R. acknowledges support from the Laboratory Directed Research and Development program under Grant No. 20180618ECR. Sample synthesis was supported by the U.S. DOE Office of Basic Energy Sciences. M. J. acknowledges support from the Institute for Materials Science, LANL. A portion of this work was performed at the NHMFL, supported by NSF Agreements No. DMR-1157490 and No. DMR-1644779 and the State of Florida. We thank J. B. Betts at the pulsed facility, and J. Billings and T. Murphy at the DC facility for their technical support. Theory work (R. M. F.) was supported by the Office of Basic Energy Sciences, US DOE, under Award No. DE-SC0012336.
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