  We constrain the coupling between axionlike particles (ALPs) and photons,
measured with the superconducting resonant detection circuit of a cryogenic
Penning trap. By searching the noise spectrum of our fixed-frequency resonant
circuit for peaks caused by dark matter ALPs converting into photons in the
strong magnetic field of the Penning-trap magnet, we are able to constrain the
coupling of ALPs with masses around $2.7906-2.7914\,\textrm{neV/c}^2$ to
$g_{a\gamma}< 1 \times 10^{-11}\,\textrm{GeV}^{-1}$. This is more than one
order of magnitude lower than the best laboratory haloscope and approximately 5
times lower than the CERN axion solar telescope (CAST), setting limits in a
mass and coupling range which is not constrained by astrophysical observations.
Our approach can be extended to many other Penning-trap experiments and has the
potential to provide broad limits in the low ALP mass range.
