  We explore the nature of X-ray sources with 70 micron counterparts selected
in the SWIRE fields ELAIS-N1, Lockman Hole and Chandra Deep Field South, for
which Chandra X-ray data are available. A total of 28 X-ray/70 micron sources
in the redshift interval 0.5<z<1.3 are selected. The X-ray luminosities and the
shape of the X-ray spectra show that these sources are AGN. Modelling of the
optical to far-infrared Spectral Energy Distribution indicates that most of
them (27/28) have a strong starburst component (>50 solar masses per year) that
dominates in the infrared. It is found that the X-ray and infrared luminosities
of the sample sources are broadly correlated, consistent with a link between
AGN activity and star-formation. Contrary to the predictions of some models for
the co-evolution of AGN and galaxies, the X-ray/70 micron sources in the sample
are not more obscured at X-ray wavelengths compared to the overall X-ray
population. It is also found that the X-ray/70 micron sources have lower
specific star-formation rates compared to the general 70 micron population,
consistent with AGN feedback moderating the star-formation in the host
galaxies.
