A2255: The first detection of filamentary polarized emission in a radio halo F. Govoni, M. Murgia, L. Feretti, G. Giovannini, D. Dallacasa and G. B. Taylor A&A, 430 1 (2005) L5-L8 Published online: 12 January 2005 DOI: 10.1051/0004-6361:200400113