Heat Capacity ofCu3Au below 4.2°K

Heat capacity measurements below 4.2°K have been made on ${\mathrm{Cu}}_3$Au in both the disordered and ordered states. It is found that ordering increases the Debye temperature of the lattice but that it leaves the electronic heat capacity substantially unchanged at a value in excess of that for free electrons. An explanation of the latter observation is proposed in terms of the changes in Brillouin zone structure that are presumed to take place on ordering. The values of Debye temperature do not agree with those obtained from low-temperature resistance measurements, but are in good accord with the value computed from the room-temperature elastic constants of ordered ${\mathrm{Cu}}_3$Au.