  Here we report on the first observational investigation of the Zeeman effect
in the G band around 4305 A. Our spectropolarimetric observations of sunspots
with the Zurich Imaging Polarimeter at the IRSOL facility confirm our previous
theoretical prediction that the molecular Zeeman effect produces measurable
circular polarization signatures in several CH lines that are not overlapped
with atomic transitions. We also find both circular and linear polarization
signals produced by atomic lines whose wavelengths lie in the G band spectral
region. Together, such molecular and atomic lines are potentially important for
empirical investigations on solar and stellar magnetism. For instance, a
comparison between observed and calculated Stokes profiles suggests that the
thermodynamical and/or magnetic properties of the photospheric regions of
sunspot umbrae are horizontally structured with a component that might be
associated with umbral dots.
