  The primary component of the multiple star phi Dra is one of the brightest
magnetic chemically peculiar stars in the northern sky. Here we report results
of a comprehensive study of the rotational photometric variability, binarity,
magnetic field geometry, and surface chemical spot structure for this star. We
derived a precise photometric rotational period of 1.71650213(21) d based on
one year of TESS nearly continuous space observations and discovered modulation
of the stellar light curve with the phase of the 127.9-d binary orbit due to
the light time travel effect. We revised parameters of the binary orbit and
detected spectroscopic contribution of the secondary. A tomographic mapping
technique was applied to the average intensity and circular polarisation
profiles derived from Narval high-resolution spectropolarimetric observations.
This analysis yielded a detailed map of the global magnetic field topology
together with the surface distributions of Si, Cr, and Fe abundances. Magnetic
mapping demonstrates that the surface field structure of phi Dra is dominated
by a distorted dipolar component with a peak field strength of 1.4 kG and a
large asymmetry between the poles. Chemical maps show an enhancement of Cr, Fe
and, to a lesser extent, Si in a series of spots encircling intersections of
the magnetic and rotational equators. These chemical spot geometries do not
directly correlate with either the local field strength or the field
inclination.
