Abstract
Measurements of magneto-transport on the organic superconductor $\kappa $-(BEDT-TTF)2I3 in magnetic fields up to 23 T at 0.48 K under hydrostatic pressures up to 9 kbar are reported. In this pronounced two-dimensional (2D) electronic system strong anomalous damping effects of Shubnikov-de Haas (SdH) oscillations are observed under very specific experimental conditions. This hints to the presence of strong electron correlations, which may occur in 2D systems. SdH high pressure experiments are reported, which show, that even 9 kbar cannot suppress the above mentioned effects in $\kappa $-(BEDT-TTF)2I3. Key words. Organic superconductors, Fermi surfaces, Magneto-quantum oscillations, Hydrostatic pressure.