Magnetic Field of Chemically Peculiar Stars from SDSS/APOGEE Infrared Survey. I. HD 13404, HD 225114, and BD $$\boldsymbol{{+}64^{\circ}}$$ 325

The paper presents spectropolarimetric monitoring of three chemically peculiar stars, HD 13404, HD 225114, and BD $${+}64^{\circ}$$ 325, whose peculiarity has been discovered during the SDSS/APOGEE IR survey. Observations were carried out with the 6-m BTA telescope equipped with a circular polarization analyzer. For the first time, the longitudinal magnetic field phase curves were constructed for these stars, and their rotational periods were refined using the TESS photometry. Significant differences in the nature of their magnetic variability were discovered: HD 13404 shows a weak modulation, probably due to the observation geometry, while HD 225114 and BD $${+}64^{\circ}$$ 325 were revealed to have a complex magnetic field topology associated with the non-uniform surface chemical distributions.