  We report on an XMM-Newton observation of the accreting millisecond pulsar,
IGR J17511-3057. Pulsations at 244.8339512(1) Hz are observed with an RMS
pulsed fraction of 14.4(3)%. A precise solution for the P_orb=12487.51(2)s
binary system is derived. The measured mass function indicates a main sequence
companion with a mass between 0.15 and 0.44 Msun. The XMM-Newton spectrum of
the source can be modelled by at least three components, multicoloured disc
emission, thermal emission from the NS surface and thermal Comptonization
emission. Spectral fit of the XMM-Newton data and of the RXTE data, taken in a
simultaneous temporal window, constrain the Comptonization parameters: the
electron temperature, kT_e=51(+6,-4) keV, is rather high, while the optical
depth (tau=1.34(+0.03,-0.06)) is moderate. The energy dependence of the pulsed
fraction supports the interpretation of the cooler thermal component as coming
from the accretion disc, and indicates that the Comptonizing plasma surrounds
the hot spots on the NS surface, which provide the seed photons. Signatures of
reflection, such as a broadened iron K-alpha emission line and a Compton hump
at 30 keV ca., are also detected. We derive from the smearing of the reflection
component an inner disc radius of ~> 40 km for a 1.4 Msun neutron star, and an
inclination between 38{\deg} and 68{\deg}. XMM-Newton also observed two type-I
X-ray bursts, probably ignited in a nearly pure helium environment. No
photospheric radius expansion is observed, thus leading to an upper limit on
the distance to the source of 10 kpc. A lower limit of 6.5 kpc can be also set
if it is assumed that emission during the decaying part of the burst involves
the whole neutron star surface. Pulsations observed during the burst decay are
compatible with being phase locked, and have a similar amplitude, than
pre-burst pulsations.
