Uniaxial stress tuning of geometrical frustration in a Kondo lattice

Hexagonal CeRhSn with paramagnetic 4f moments on a distorted kagome lattice displays zero-field quantum critical behavior related to geometrical frustration. We report high-resolution thermal expansion and magnetostriction measurements under multiextreme conditions such as uniaxial stress up to 200 MPa, temperatures down to 0.1 K, and magnetic fields up to 10 T. Under uniaxial stress along the a direction, quantum criticality disappears and a complex magnetic phase diagram arises with a sequence of phases below 1.2 K and fields between 0 and 3 T (parallel to a). Since the Kondo coupling increases with stress, which alone would stabilize paramagnetic behavior in CeRhSn, the observed order arises from the release of geometrical frustration by in-plane stress.