We report the discovery of an eclipsing polar , 2XMMi J225036.9+573154 , using XMM-Newton .
It was discovered by searching the light curves in the 2XMMi catalogue for objects showing X-ray variability .
Its X-ray light curve shows a total eclipse of the white dwarf by the secondary star every 174 mins .
An extended pre-eclipse absorption dip is observed in soft X-rays at \phi =0.8–0.9 , with evidence for a further dip in the soft X-ray light curve at \phi \sim 0.4 .
Further , X-rays are seen from all orbital phases ( apart from the eclipse ) which makes it unusual amongst eclipsing polars .
We have identified the optical counterpart , which is faint ( r =21 ) , and shows a deep eclipse ( > 3.5 mag in white light ) .
Its X-ray spectrum does not show a distinct soft X-ray component which is seen in many , but not all , polars .
Its optical spectrum shows H \alpha in emission for a fraction of the orbital period .