  We investigate an oblique spacetime crystal realized by a monoatomic crystal
in which a mode of sound propagates. We provide a systematic analysis of the
crystal and obtain the corresponding band structure, based on which the
electron dynamics under an external electric field is studied. Several unique
band topologies are revealed, which lead to novel Floquet-Bloch oscillations in
the electron's motion. We also discover intraband Zener tunneling in the
oblique spacetime crystal beyond the adiabatic limit, which effectively
converts between the different band topologies. Our results indicate the
possibility of a prototypical quantum acoustoelectric generator that converts
energy between the sound wave and a DC electric field in quantized units.
