A composite is provided having an electrically conducting Al matrix andelongated filaments comprising Ca and/or Sr and/or Ba disposed in the matrixand extending along a longitudinal axis of the composite. The filaments initially comprise Ca and/or Sr and/or Ba metal or alloy and then may be reacted with the Al matrix to form a strengthening intermetallic compound comprising Al andCa and/or Sr and/or Ba. The composite is useful as a long-distance, high voltage power transmission conductor.