[1] Helmholtz Zentrum Berlin Mat & Energie, Elektronenspeicherring BESSY 2, Albert Einstein Str 15, D-12489 Berlin, Germany
[2] Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany
[3] Natl Acad Sci Ukraine, Inst Problems Mat Sci, Krzhyzhanovsky Str 3, UA-03142 Kiev, Ukraine
[4] Slovak Acad Sci, Inst Expt Phys, Watsonova 47, Kosice 04001, Slovakia
[5] Tech Univ Dresden, Inst Festkorperphys, D-01062 Dresden, Germany
[6] Leibniz Inst Festkorper & Werkstoffforsch Dresden, Helmholtzstr 20, D-01069 Dresden, Germany