  Axion dark matter (DM) constitutes an oscillating background that violates
parity and time-reversal symmtries. Inside piezoelectric crystals, where parity
is broken spontaneously, this axion background can result in a stress. We call
this new phenomenon "the piezoaxionic effect". When the frequency of axion DM
matches the natural frequency of a bulk acoustic normal mode of the
piezoelectric crystal, the piezoaxionic effect is resonantly enhanced and can
be read out electrically via the piezoelectric effect. We explore all axion
couplings that can give rise to the piezoaxionic effect -- the most promising
one is the defining coupling of the QCD axion, through the anomaly of the
strong sector. We also point our another, subdominant phenomenon present in all
dielectrics, namely the "electroaxionic effect". An axion background can
produce an electric displacement field in a crystal which in turn will give
rise to a voltage across the crystal. The electroaxionic effect is again
largest for the axion coupling to gluons. We find that this model independent
coupling of the QCD axion may be probed through the combination of the
piezoaxionic and electroaxionic effects in piezoelectric crystals with aligned
nuclear spins, with near-future experimental setups applicable for axion masses
between $10^{-11}\,\mathrm{eV}$ and $10^{-7}\,\mathrm{eV}$, a challenging range
for most other detection concepts.
