In a previous work, the simplest decomposition without residual part of a generic deformed Lie product f has been interpreted as the representation of a (2, 0) version of some EM field in M(4, C). This document (in the French language) is precising the conditions of validity for this interpretation. It proves: (i) that isotropic EM fields are compatible with it; (ii) again, the existence of Lie algebras; (iii) that the passage between the simplest decomposition of f and the antisymmetric decomposition of (f o f) (both without residual part) is an EM transition involving isotropic EM fields presumably linked with natural electromagnetic oscillations in Maxwell's vacuum. Since their effective nature remains to be identified, one is pushed to propose a new interpretation for f involving the dual representation of any EM field.Key words: representations of the EM fields, Lie algebras, evolution.