  Dark Matter (DM) and Dark Energy (DE) can be both described in terms of
ultra-light Pseudo-Goldstone-Bosons (PGB) with masses m_{DM} ~ 10^{-23}eV and
m_{DE} <= 10^{-33}eV respectively. Following Barbieri et al, we entertain the
possibility that a PGB exists with mass m_I intermediate between these two
limits, giving a partial contribution to DM. We evaluate the related effects on
the power spectrum of the matter density perturbations and on the cosmic
microwave background and we derive the bounds on the density fraction, f_I, of
this intermediate field from current data, with room for a better sensitivity
on f_I in the near future. We also give a simple and unified analytic
description of the free streaming effects both for an ultra-light scalar and
for a massive neutrino.
