  We present results on the spectroscopic analysis of XMM-Newton EPIC data of
the central 0.5/h_50 Mpc regions of the clusters of galaxies Coma, A1795 and
A3112. The temperature of the hot intracluster gas as determined by modeling
the 2 - 7 keV PN and MOS data is consistent with that inferred from the
FeXXV-FeXXVI line ratio. A significant warm emission component at a level above
the systematic uncertainties is evident in the data and confirmed by ROSAT PSPC
data for Coma and A1795. The non-thermal origin of the phenomenon cannot be
ruled out at the current level of calibration accuracy, but the thermal model
fits the data significantly better, with temperatures in the range of 0.6 --
1.3 keV and electron densities of the order of 10^{-4} -- 10^{-3} cm^{-3}. In
the outer parts of the clusters the properties of the warm component are
marginally consistent with the results of recent cosmological simulations,
which predict a large fraction of the current epoch's bayons located in a
warm-hot intergalactic medium (WHIM). However, the derived densities are too
high in the cluster cores, compared to WHIM simulations, and thus more
theoretical work is needed to fully understand the origin of the observed soft
X-ray excess.
