  We report an extended search for the axion dark matter using the CAPP18T
haloscope. The CAPP18T experiment adopts innovative technologies of a
high-temperature superconducting magnet and a Josephson parametric converter.
The CAPP18T detector was reconstructed after an unexpected incident of the
high-temperature superconducting magnet quenching. The system reconstruction
includes rebuilding the magnet, improving the impedance matching in the
microwave chain, and mechanically readjusting the tuning rod to the cavity for
improved thermal contact. The total system noise temperature is $\sim$0.6\,K.
The coupling between the cavity and the strong antenna is maintained at $\beta
\simeq 2$ to enhance the axion search scanning speed. The scan frequency range
is from 4.8077 to 4.8181 GHz. No significant indication of the axion dark
matter signature is observed. The results set the best upper bound of the
axion-photon-photon coupling ($g_{a\gamma\gamma}$) in the mass ranges of 19.883
to 19.926\,$\mu$eV at $\sim$0.7$\times|g_{a\gamma\gamma}^{\text{KSVZ}}|$ or
$\sim$1.9$\times|g_{a\gamma\gamma}^{\text{DFSZ}}|$ with 90\,\% confidence
level. The results demonstrate that a reliable search of the high-mass dark
matter axions can be achieved beyond the benchmark models using the technology
adopted in CAPP18T.
