Nonmonotonic conductivity change of C60 fullerene crystals under dynamic compression up to 300 kbar

In the present work the conductivity of fullerene C$_{60}$ crystals has been measured under smooth shock wave quasi-isentropic loading conditions up to 30 GPa at initial temperature T=293 K. Not monotone behavior of conductivity has been revealed under compression of crystal with pressure increasing: -at first conductivity grows by many orders then it falls very fast. Conductivity increasing is explained by decreasing of bandgap of C$_{60}$ under compression whereas conductivity decreasing can be explained on the assumption that the energy barrier of polymerization of C$_{60}$ reduces with pressure increasing approximately in the same measure as band-gap energy. Research is financially supported by the Russian foundation for basic research, the grant N 03-02-16322, the grant of the President of Russia NS 1938.2003.2, and program of basic researches of the Russian Academy of Science ``Thermophysics and mechanics of processes at high energy densities.''