Electronic nematics are exotic states of matter where electronic interactionsbreak a rotational symmetry of the underlying lattice, in analogy to thedirectional alignment without translational order in nematic liquid crystals.Intriguingly such phases appear in the copper- and iron-based superconductors,and their role in establishing high-temperature superconductivity remains anopen question. Nematicity may take an active part, cooperating or competingwith superconductivity, or may appear accidentally in such systems. Here wepresent experimental evidence for a phase of nematic character in the heavyfermion superconductor CeRhIn5. We observe a field-induced breaking of theelectronic tetragonal symmetry of in the vicinity of an antiferromagnetic (AFM)quantum phase transition at Hc~50T. This phase appears in out-of-plane fieldsof H*~28T and is characterized by substantial in-plane resistivity anisotropy.The anisotropy can be aligned by a small in-plane field component, with noapparent connection to the underlying crystal structure. Furthermore noanomalies are observed in the magnetic torque, suggesting the absence ofmetamagnetic transitions in this field range. These observations are indicativeof an electronic nematic character of the high field state in CeRhIn5. Theappearance of nematic behavior in a phenotypical heavy fermion superconductorhighlights the interrelation of nematicity and unconventionalsuperconductivity, suggesting nematicity to be a commonality in such materials.
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