Abstract: A material provides protection against electrical overstress transients having rise times as rapid as a few nanoseconds or less. The material comprises a matrix formed of a mixture of separate particles of conductive materials and separate particles of semiconductor materials coated with insulating material to provide chains of the particles within the matrix with interparticle separation distances along the chains less than several hundred angstroms, thereby to permit quantum-mechanical tunneling of electrons between the separate particles in response to high energy electrical transients.