  We present a study of the accretion flow to the intermittent accreting
millisecond pulsar, HETE J1900.1-2455, based on observations performed
simultaneously by XMM-Newton and RXTE. The 0.33-50 keV spectrum is described by
the sum of a hard Comptonized component originated in an optically thin
{\tau}~1 corona, a soft kTin~0.2 keV component interpreted as accretion disc
emission, and of disc reflection of the hard component. Two emission features
are detected at energies of 0.98(1) and 6.58(7) keV, respectively. The latter
is identified as K{\alpha} transition of Fe XXIII-XXV. A simultaneous detection
in EPIC-pn, EPIC-MOS2, and RGS spectra favours an astrophysical origin also for
the former, which has an energy compatible with Fe-L{\alpha} and helium-like
Ne-K{\alpha} transitions. Broadness of the two features suggests a common
origin, resulting from reflection in an accretion disc with inclination of
(30+4{\deg}), and extending down to Rin=25(+16,-11) gravitational radii from
the compact object. However, the strength of the feature at lower energy
measured by EPIC-pn cannot be entirely reconciled with the amplitude of the Fe
K{\alpha} line, hampering the possibility of describing it in terms of a
broad-band reflection model, and preventing a firm identification. Pulsations
at the 377.3 Hz spin frequency could not be detected, with an upper limit of
0.4% at 3-{\sigma} c.l. on the fractional amplitude. We interpret the inner
disc radius estimated from spectral modelling and the lack of significant
detection of coherent X-ray pulsations as an indication of a disc accretion
flow truncated by some mechanism connected to the overall evolution of the
accretion disc, rather than by the neutron star magnetic field. This is
compatible with the extremely close similarity of spectral and temporal
properties of this source with respect to other, non pulsing atoll sources in
the hard state.
