Possible anomalous quantum Hall effect at high quantum numbers and temperatures up to 4.2K

Measurement data of the quantum Hall effect in GaAs-GaxAl1-xAs heterostructures for different directions of the magnetic field and the sample current relative to each other are added and subtracted. The results, instead of being equal to zero, show reproducible structures which are highly correlated to fractions of the filling factor nu. In different samples with mobilities of nearly 4.5 X 10(5) cm(2) V-1 s(-1) we observed structures at filling factors of the nu = p/q series with q = 2, 3,4, 5, 7, 9. 11 at temperatures of 1.2 K and 4.2 K in the range 2 mu A to 15 mu A sample current. The structures were found to be independent of the sample current. Equivalent structures were observed for the voltage drop U-p parallel to the sample current using the same method and by investigation of the second derivative of the Hall voltage against the magnetic flux density B. By this method we found structures at filling factors up to 19/2 at T = 1.2 K.