  We measured mid-infrared polarization of protoplanetary discs to gain new
insight into their magnetic fields. Using CanariCam at the 10.4 m Gran
Telescopio Canarias, we detected linear polarization at 8.7, 10.3, and 12.5
$\mu$m from discs around eight Herbig Ae/Be stars and one T-Tauri star. We
analyzed polarimetric properties of each object to find out the most likely
interpretation of the data. While the observed mid-infrared polarization from
most objects is consistent with polarized emission and/or absorption arising
from aligned dust particles, we cannot rule out polarization due to dust
scattering for a few objects in our sample. For those objects for which
polarization can be explained by polarized emission and/or absorption, we
examined how the derived magnetic field structure correlates with the disc
position angle and inclination. We found no preference for a certain type of
magnetic field. Instead, various configurations (toroidal, poloidal, or
complex) are inferred from the observations. The detection rate (64 per cent)
of polarized mid-infrared emission and/or absorption supports the expectation
that magnetic fields and suitable conditions for grain alignment are common in
protoplanetary discs around Herbig Ae/Be stars.
