  Recently, an approach for metallic superlattices based on the finite periodic
systems theory was introduced \cite{Pereyra2020}. Unlike most, if not all, of
the published approaches that are valid in the $n \rightarrow \infty $ limit,
the finite periodic approach is valid for any natural number $n$ and allows one
to determine analytical expressions for scattering amplitudes and dispersion
relations. It was shown, for frequencies below $\omega_{p}$ and large
metallic-layer thickness, that under the common assumption that fields inside
conductors move along the so-called "true" angle that defines the orientation
of the constant-phase planes, anomalous results appear with an apparent parity
effect. This issue is addressed here and it is shown that those results are due
to the lack of unitarity and the underlying phenomena of absorption and loss of
energy. Two compatible approaches are presented here to solve the lack of
unitarity and to account for the absorption phenomenon. We show that by keeping
the complex angles, the principle of flux conservation is fully satisfied,
above and below $\omega_p$. This approach, free of assumptions, gives us light
to improve the formalism when the real angle assumption is made. We show that
by taking into account the induced currents and the requirement of flux
conservation, we end up with an improved approach, with new Fresnel and
transmission coefficients, fully compatible with those of the complex-angle
approach.
