What is causing this voltage overshoot?
i need some leads on the cause of the voltage overshoot when there is
  signinfant current at the commutation


With perfect MOSFETs, switching from high to low with zero switching time, there will be no theoretical overshoot. Reality is a different matter. 

You have current in the inductor and there is a brief period in time where there is a gap in the switching between one MOSFET and the other. That means the current in the inductor will create a spike and the only thing dampening that spike is the output capacitance of the MOSFETs. This will reduce the effect of the spike and turn it into a high frequency decaying sinewave.