A positive temperature coefficient (PTC) superimposed impedance polymeric (SIP) compound including an electrically insulating matrix essentially consisting of a siloxane polymer in addition to first and second electrically conductive particles having different properties with respect to surface energies and electrical conductivities. A multi-layered, ZPZ, foil including a PTC SIP compound of the invention present between two metal foils, thereby forming a conductive composite body. A multi-layered device, including an essentially flat composite body made up from a PTC SIP compound according to the invention, two electrode layers adhering to the surfaces of the composite body, the electrode layers being metal foils prepared to connect to electrodes.