A marker stake for locating a boundary reference point on a sports field can be buried and out of sight when not in use, and then quickly located using an electronic receiver which detects a signal emitted by an electronic marker in the marker stake. The power module is electrically connected with extraction lines, which extend from a coil wound around the stator, and supplies a drive current to the coil. In the step, at least a first carbon material and the metal material Z mixed into an elastomer, and dispersing the first carbon material and the metal material Z by applying a shear force to obtain a composite elastomer, the metal material Z having a melting point lower than a melting point of the first carbon material.