  We present an XMM-Newton catalogue of BL Lac X-ray, optical, and UV
properties based on cross-correlation with the 1151 BL Lacs listed in the fifth
edition of the Roma-BZCAT. We searched for the X-ray counterparts to these
objects in the field of view of all pointed observations in the XMM-Newton
archive over nearly 20 years of mission. The cross-correlation yields a total
of 310 XMM-Newton fields which correspond to 103 different BL Lacs. We
homogeneously analysed data from the three EPIC cameras (X-ray) and
OM(optical/UV) using the XMM-Newton SAS software, and produced images, light
curves, and spectral products for BL Lacs detected in any of the three EPIC
cameras. We tested two different phenomenological models, log parabola and
power law, with different variations of the absorbing column density and
extracted their parameters. We derived time-variability information from the
light curves following well-established statistical methods and quantified
variability through statistical indicators. OM magnitudes and fluxes were
computed wherever possible. We see that the log parabola model is preferred
over the power law model for sources showing higher fluxes, which might
indicate that curvature is intrinsic to BL Lacs and is only seen when the flux
is high. We present the results of our analysis as a catalogue of X-ray
spectral properties of the sample in the 0.2-10 keV energy band as well as in
the optical/UV band. We complete the catalogue with multi-wavelength
information at radio and gamma-ray energies.
