  We performed J- and R-band linear polarimetry with the 4.2 m William Herschel
Telescope at the Observatorio del Roque de los Muchachos and with the 1.6 m
telescope at the Observat\'orio do Pico dos Dias, respectively, to derive the
magnetic field geometry of the diffuse molecular cloud surrounding the embedded
protostellar system NGC 1333 IRAS 4A. We obtained interstellar polarization
data for about two dozen stars. The distribution of polarization position
angles has low dispersion and suggests the existence of an ordered magnetic
field component at physical scales larger than the protostar. Some of the
observed stars present intrinsic polarization and evidence of being young
stellar objects. The estimated mean orientation of the interstellar magnetic
field as derived from these data is almost perpendicular to the main direction
of the magnetic field associated with the dense molecular envelope around IRAS
4A. Since the distribution of the CO emission in NGC 1333 indicates that the
diffuse molecular gas has a multi-layered structure, we suggest that the
observed polarization position angles are caused by the superposed projection
along the line of sight of different magnetic field components.
