Known as a type-II Weyl fermion, the quasiparticle breaks a rule called Lorentz symmetry, which states that the laws of physics are the same no matter the observer’s perspective, whether moving or stationary. For a real particle, violating Lorentz symmetry would be an unallowable faux pas, but for quasiparticles, the rules are looser, so type-II Weyl fermions can behave in a way a normal particle wouldn’t. In the new study, Hasan and colleagues measured the relationship between the energy and momentum of the quasiparticles, showing that they were consistent with type-II Weyl fermions.