  A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs,
recently announced the discovery of two rare rigidly rotating magnetosphere
stars, HD345439 and HD23478. Near-infrared spectra of these objects revealed
emission-line behavior identical to that previously discovered in the
helium-strong star sigma Ori E, which has a strong magnetic field and rotates
fast. A single spectropolarimetric observation of HD345439 with FORS2 at the
VLT in 2014 over 88min indicated that HD345439 may host a strong, rapidly
varying magnetic field. In this work, we present the results of our
spectropolarimetric monitoring of this star with FORS2, which revealed the
presence of a strong longitudinal magnetic field dominated by a dipolar
component. The analysis of spectral variability indicates an opposite behaviour
of He and Si lines, which is usually attributed to differences in the
distribution of surface He and Si abundance spots.
