THIRD-HARMONIC EMISSION IN <font>MgB</font>2 SUPERCONDUCTOR AT MICROWAVE FREQUENCIES

We report a set of experimental results on microwave third-harmonic emission by MgB 2 superconductor. We have investigated third-harmonic signals as a function of temperature, input power level and intensity of the static magnetic field. We show that different mechanisms are responsible for third-harmonic emission at temperatures near T c and far below T c , similarly to what has been obtained in other high- T c superconductors.