Quantum nematic in a colossal magnetoresistance material

Quantum nematic phases are analogous to classical liquid crystals. Like liquid crystals, which break the rotational symmetries of space, their quantum analogues break the point-group symmetry of the crystal due to strong electron-electron interactions, as in quantum Hall states, Sr3Ru2O7, and high temperature superconductors. Here, we present angle resolved magnetoresistance (AMRO) measurements that reveal a quantum nematic phase in the hexaboride EuB6. We identify the region in the temperature-magnetic field phase diagram where the magnetoresistance shows two-fold oscillations instead of the expected four-fold pattern. This is the same region where magnetic polarons were previously observed, suggesting that they drive the nematicity in EuB6. This is also the region of the phase diagram where EuB6 shows a colossal magnetoresistance (CMR). This novel interplay between magnetic and electronic properties could thus be harnessed for spintronic applications.