Energy, momentum and mass transfer by an electromagnetic wave in a negative refraction medium

The problem of photon momentum in a refracting medium is discussed. For the particular case of a negative refraction medium it is shown that the relation $P=\hbar k$ and $\Delta M=E/c^2$ cannot hold simultaneously and that light pressure is replaced by light attraction. It is also shown that the Abraham energy-momentum tensor is not in fact a tensor because of its lack of relativistic invariance.