We report the results of a comprehensive study of the spectroscopic binary (SB2) system HD 34736 hosting two chemically peculiar (CP) late B-type stars. Using new and archival observational data, we characterize the system and its components, including their rotation and magnetic fields. Fitting of the radial velocities yields Porb = 83.d 219(3) and e = 0.8103(3). The primary component is a CP He-wk star with Teff A = 13000 ± 500 K and υe sin i = 75 ± 3 km s−1 , while the secondary exhibits variability of Mg and Si lines, and has Teff B = 11500 ± 1000 K and υe sin i = 110–180 km s−1 . Transiting Exoplanet Survey
Satellite and Kilodegree Extremely Little Telescope photometry reveal clear variability of the primary component with a rotational period ProtA = 1.d 279 988 5(11), which is lengthening at a rate of 1.26(6) s yr−1 . For the secondary, ProtB = 0.d 522 693 8(5),
reducing at a rate of −0.14(3) s yr−1 . The longitudinal component 〈Bz 〉 of the primary’s strongly asymmetric global magnetic field varies from −6 to +5 kG. Weak spectropolarimetric evidence of a magnetic field is found for the secondary star. The
observed X-ray and radio emission of HD 34736 may equally be linked to a suspected T Tau-like companion or magnetospheric emission from the principal components. Given the presence of a possible third magnetically active body, one can propose that
the magnetic characteristics of the protostellar environment may be connected to the formation of such systems