  In this paper, we show that a general method introduced by Fu and Mielke
allows to give a complete answer on the existence and uniqueness of a subsonic
solution describing the propagation of surface waves in an isotropic half space
modelled with the linear theory of isotropic elastic materials with
micro-voids. Our result is valid for the entire class of materials admitting
real wave propagation which include auxetic materials (negative Poisson's
ration) and composite materials with negative-stiffness inclusions (negative
Young's modulus). Moreover, the used method allows to formulate a simple and
complete numerical strategy for the computation of the solution.
