Total electrical conductivities and transference numbers of the AgxCu1
-xI in the alpha-phase were measured as a function of temperature and
composition. In this phase, it has been recognized that both Ag and Cu
ions could be mobile and, in addition, the activation energies for bo
th mobile ions are nearly the same. A structure refinement for this ph
ase shows that both Ag and Cu ions vibrate at the 12d site with a larg
e anharmonicity. However, the lattice constant obeys Vegard's law. Thi
s result indicates that both mobile ions have the same conducting path
although their amplitudes of anharmonic thermal vibrations are differ
ent.