A rod and a method of forming a rod are provided. The rod includes a gathered sheet of material circumscribed by a wrapper, in which the sheet of material is a co-laminated sheet comprising a layer of an aerosol-forming material and a layer of a thermally-conductive material and in which the wrapper is a metal foil. The method includes providing a continuous co-laminated sheet including an aerosol-forming material and a thermally-conductive material; gathering the co-laminated sheet transversely relative to its longitudinal axis; circumscribing the gathered co-laminated sheet with a metal foil wrapper to form a continuous rod; and severing the continuous rod into a plurality of discrete rods.