Fractional quantum Hall effect at suppressed energy gap

In the fractional quantum Hall effect regime we measure diagonal ($\rho _{xx}$) and Hall ($\rho _{xy}$) magnetoresistivity tensor components of two-dimensional electron system (2DES) in gated GaAs/Al$_x$Ga$_{1-x}$As heterojunctions, together with capacitance between 2DES and the gate. We observe 1/3- and 2/3-fractional quantum Hall effect at rather low magnetic fields where corresponding fractional minima in the thermodynamical density of states have already disappeared implying suppression of the quasiparticle energy gaps.