  Dark matter-baryon interactions can cool the baryonic fluid, which has been
shown to modify the cosmological 21-cm global signal. We show that in a
two-component dark sector with an interacting millicharged component, dark
matter-baryon scattering can produce a 21-cm power spectrum signal with
acoustic oscillations. The signal can be up to three orders of magnitude larger
than expected in $\Lambda$CDM cosmology, given realistic astrophysical models.
This model provides a new-physics target for near-future experiments such as
HERA or NenuFAR, which can potentially discover or strongly constrain the dark
matter explanation of the putative EDGES anomaly.
