Looking for a possible breakdown of local Lorentz invariance for electromagnetic phenomena: Theory and first experimental results

We propose a new electromagnetic test of breakdown of local Lorentz invaria nce. It is based essentially on the detection of a non-zero force between a circular steady current and a charge, both at rest in the Earth frame. A p reliminary experimental run gave a positive evidence for such an effect, wh ich appears strongly dependent on the orientation of the circuit. Possible theoretical interpretations are briefly discussed.