J06587-5558: a very unusual polarized radio source

We have found a peculiar radio source, J06587 - 5558, in the field of one of the hottest known clusters of galaxies, 1E 06572 - 56. It is slightly extended and highly polarized (54 per cent at 8.8 GHz), and has a very steep spectrum, with α ~ -1 at 1.3 GHz, steepening to ~ -1 .5 at 8.8 GHz (S∝vα). No extragalactic sources are known with such high integrated polarization, and sources with spectra as steep as this are rare. In this Letter, we report the unusual properties of the source J06587 - 5558 and speculate on its origin and optical identification.