  Context: Finding Active Galactic Nuclei (AGN) behind the Magellanic Clouds
(MCs) is difficult because of the high stellar density in these fields.
Although the first AGN behind the Small Magellanic Cloud (SMC) were reported in
the 1980s, it is only recently that the number of AGN known behind the SMC has
increased by several orders of magnitude. Aims: The mid-infrared colour
selection technique has been proven to be an efficient means of identifying
AGN, especially obscured sources. The X-ray regime is complementary in this
regard and we use XMM-Newton observations to support the identification of AGN
behind the SMC. Methods: We present a catalogue of AGN behind the SMC by
correlating an updated X-ray point source catalogue from our XMM-Newton survey
of the SMC with already known AGN from the literature as well as a list of
candidates obtained from the ALLWISE mid-infrared colour selection criterion.
We studied the properties of the sample with respect to their redshifts,
luminosities and X-ray spectral characteristics. We also identified the
near-infrared counterpart of the sources from the VISTA observations. Results:
The redshift and luminosity distributions of the sample (where known) indicate
that we detect sources from nearby Seyfert galaxies to distant and obscured
quasars. The X-ray hardness ratios are compatible with those typically expected
for AGN. The VISTA colours and variability are also consistent in this regard.
A positive correlation was observed between the integrated X-ray flux (0.2--12
keV) and the ALLWISE and VISTA magnitudes. We further present a sample of new
candidate AGN and candidates for obscured AGN. All of these make an interesting
subset for further follow-up studies. An initial spectroscopic follow-up of 6
out of the 81 new candidates showed all six sources are active galaxies, albeit
two with narrow emission lines.
