1. Institute of Experimental Physics, Warsaw University, Hoża 69, 00-681 Warsaw, Poland
2. Groupe d'Etude des Semiconducteurs, CNRS-UMR5650 Université Montpellier 2, Montpellier, France
3. CNRS - CRHEA, rue Bernard Grégory, Valbonne-Sophia-Antipolis, France
4. High Pressure Research Center, Polish Academy of Sciences, Sokołowska 29/37, Warsaw, Poland