  The mechanical behaviour of Mg-Al alloys can be largely improved by the
formation of an intermetallic Laves phase skeleton, in particular the creep
strength. Recent nanomechanical studies revealed plasticity by dislocation
glide in the (Mg,Al)$_2$Ca Laves phase, even at room temperature. As
strengthening skeleton, this phase remains, however, brittle at low
temperature. In this work, we present experimental evidence of slip transfer
from the Mg matrix to the (Mg,Al)$_2$Ca skeleton at room temperature and
explore associated mechanisms by means of atomistic simulations. We identify
two possible mechanisms for transferring Mg basal slip into Laves phases
depending on the crystallographic orientation: a direct and an indirect slip
transfer triggered by full and partial dislocations, respectively. Our
experimental and numerical observations also highlight the importance of
interfacial sliding that can prevent the transfer of the plasticity from one
phase to the other.
