  Evidence for a spectral flattening of the supernova remnant (SNR) HB3
(G132.7+1.3) was recently claimed in literature based on previously published
total flux density data, and the flattening was further interpreted as the
discovery of thermal bremsstrahlung emission in the shell of HB3. A spectral
flattening has never been observed from any SNR before. Reliable observations
of HB3 at frequencies above 3000 MHz are crucial to confirm such a spectral
behaviour. We extracted 4800 MHz total intensity and polarisation data of HB3
from the Sino-German 6 cm polarisation survey of the Galactic plane made with
the Urumqi 25 m telescope, and analysed the spectrum of HB3, together with
Effelsberg data at 1408 MHz and 2675 MHz. We found an overall spectral index of
HB3 of alpha=-0.61+-0.06 between 1408 MHz and 4800 MHz, similar to the index at
lower frequencies. There is no spectral flattening at high frequencies. We
detected strong polarised emission from HB3 at 4800 MHz. Our 4800 MHz data show
a tangential field orientation in the HB3 shell.
