We have prepared a set of polycrystalline samples of the metallic copper oxide La 4 BaCu 5Àx Co x O 13þd (0 x 0.35) and have measured the resistivity from 4 to 800 K. All the resistivities show metallic temperature dependence with a small magnitude less than 2 mX cm at 800 K, indicating that the metallic conduction is robust against impurities. The robust metallic conduction further suggests that this class of oxide is a promising candidate for electrical leads at high temperature, which might replace platinum. A detailed measurement and analysis on the Hall resistivity have revealed that at least two components are responsible for the electrical conduction, in which a large number of electrons of moderate mobility coexist with a much smaller number of holes of extremely high mobility. This large electron density well screens the impurity potential and retains the metallic conduction against 7% impurity doping. V C 2015 AIP Publishing LLC.