  Disorder or quasi-disorder is known to favor the localization in many-body
Bose systems. Here in contrast, we demonstrate an anomalous delocalization
effect induced by incommensurability in quasiperiodic lattices. Loading
ultracold atoms in two shallow periodic lattices with equal amplitude and
either equal or incommensurate spatial periods, we show the onset of a Mott
transition not only in the periodic case but also in the quasiperiodic case.
Upon increase of the incommensurate component of the potential we find that the
Mott insulator turns into a delocalized superfluid. Our experimental results
agree with quantum Monte Carlo calculations, showing anomalous delocalization
induced by the interplay between the commensuration and interaction.
