  We study the dynamics of few interacting bosons in a one-dimensional lattice
with dc bias. In the absence of interactions the system displays single
particle Bloch oscillations. For strong interaction the Bloch oscillation
regime reemerges with fractional Bloch periods which are inversely proportional
to the number of bosons clustered into a bound state. The interaction strength
is affecting the oscillation amplitude. Excellent agreement is found between
numerical data and a composite particle dynamics approach. For specific values
of the interaction strength a particle will tunnel from the interacting cloud
to a well defined distant lattice location.
