The frequency and time dependence of the ac conductivity were measured within incommensurate phase in the frequency range 10(1)-10(7) Hz and analyzed. The electrical conductivity decreases with decreasing temperature, then saturates in mentioned temperature interval. The ac conductivity is proportional to w(s). The value f s decreases with increasing temperature which suggests hopping conduction mechanism. The time dependence of the conductivity exhibited exponential decay. It shows two conductivity relaxations in mentioned temperature interval. Moreover, the characteristic relaxation times decrease with decreasing annealing temperature. The two different relaxation times refer to two different incommensurate ordering in mentioned temperature interval. (c) 2005 WILEY-VCH Verlag GmbH T Co. KGaA, Weinheim.