  We present an XMM-Newton observation of the radio-quiet quasar Q0056-363
(z=0.162). This is the first time that this quasar is observed in the hard
X-ray range (above 2 keV). We find that Q0056-363 is a powerful X-ray quasar,
with a 0.3-12 keV unabsorbed luminosity of about 1.2 x 10^45 erg s-1 with the
largest part (~67%) emitted below 2 keV. The spectrum reveals a large
featureless soft X-ray excess below 2 keV and a strong broad FeKalpha line at
6.4 keV (in the quasar frame). The FeK alpha line is due to low to moderate
ionization states of iron (i.e., < Fe XVII), with an equivalent width of about
250 eV and a velocity width of about 25,000 km s-1. Q0056-363 is presently the
most luminous AGN known to exhibit such a broad and intense FeKalpha line
profile from near neutral iron. The line can be fitted with a relativistic
profile from an accretion disc around either a Schwarzschild (non-rotating) or
a Kerr (rotating) black hole. A combination of two thermal Comptonization
components and a disc reflection model is favored to explain both the continuum
over the energy range 0.3-12 keV and the FeK alpha line. A patchy corona
covering a large part of the inner disc surface is needed in order to be
compatible with the accretion rate inferred from the spectral energy
distribution of Q0056-363, unless the mass of the black hole is much higher
than about 5 x 10^8 M_odot.
