The electrical resistivity vs. both the temperature and hydrogen pressure presents a characteristic S-shape curve with a minimum and a maximum of the resistivity. This behaviour permitted to recognize three stages: (1) introduction of H into Pd-Ag lattice up to a well-defined H/M ratio increases the resistivity; (2) further uptake of hydrogen with a decrease of resistivity until a higher H/M ratio; (3) above this higher H/M ratio the resistivity increases sharply.
The behaviour of the electrical resistivity is discussed in details by considering the hydrogen uploading into the metal lattice, its effect on the conduction electrons and the scattering of the hydrogen atoms into the metal lattice.