Colossal piezoresistance in narrow-gap Eu5In2Sb6

A remarkably large reduction in the electrical resistivity of the quantum material Eu${}₅$In${}₂$Sb${}₆$ is discovered as a function of applied uniaxial pressure. This phenomenon, called colossal piezoresistance, is linked to a colossal magnetoresistance effect previously observed in this material. There is a common origin for the two phenomena, namely the interaction-driven formation of magnetic metallic clusters in semiconducting Eu${}₅$In${}₂$Sb${}₆$. These results will aid our understanding of colossal magnetoresistance and piezoresistance effects in a broad set of quantum materials.