In a non-convex polyhedral domain, we describe the local trace (i.e. defined on a face) of the normal derivative of an L2 function, with L2 Laplacian. We then provide generalized integration by parts formulae for the Laplace, divergence and curl operators. Finally, these results allow us to split electromagnetic fields into regular and singular parts, which can be characterized. © 2005 Académie des sciences. Published by Elsevier SAS. All rights reserved.