  MAXI J1820+070, a black hole candidate first detected in early March 2018,
was observed by XMM-Newton during the outburst rise. In this letter we report
on the spectral and timing analysis of the XMM-Newton X-ray and UV data, as
well as contemporaneous X-ray data from the Swift satellite. The X-ray spectrum
is well described by a hard thermal Comptonization continuum. The XMM-Newton
X-ray light curve shows a pronounced dipping interval, and spectral analysis
indicates that it is caused by a moderately ionized partial covering absorber.
The XMM-Newton/OM U-filter data does not reveal any signs of the 17 hr orbital
modulation that was seen later on during the outburst decay. The UV/X-ray cross
correlation function shows a complex shape, with a peak at positive lags of
about 4 seconds and a pre-cognition dip at negative lags, which is absent
during the X-ray dipping episode. Such shape could arise if the UV emission
comes partially from synchrotron self-Compton emission near the black hole, as
well as from reprocessing of the X-rays in the colder accretion disc further
out.
