  The aim of this study is to carry out an abundance determination, to search
for spectral variability and for the presence of a weak magnetic field in the
typical PGa star HD19400. High-resolution, high signal-to-noise HARPS
spectropolarimetric observations of HD19400 were obtained at three different
epochs in 2011 and 2013. For the first time, we present abundances of various
elements determined using an ATLAS12 model, including the abundances of a
number of elements not analysed by previous studies, such as Ne I, Ga II, and
Xe II. Several lines of As II are also present in the spectra of HD19400. To
study the variability, we compared the behaviour of the line profiles of
various elements. We report on the first detection of anomalous shapes of line
profiles belonging to Mn and Hg, and the variability of the line profiles
belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the
variability of the line profiles of these elements is caused by their
non-uniform surface distribution, similar to the presence of chemical spots
detected in HgMn stars. The search for the presence of a magnetic field was
carried out using the moment technique and the SVD method. Our measurements of
the magnetic field with the moment technique using 22 Mn II lines indicate the
potential existence of a weak variable longitudinal magnetic field on the first
epoch. The SVD method applied to the Mn II lines indicates <B_z>=-76+-25G on
the first epoch, and at the same epoch the SVD analysis of the observations
using the Fe II lines shows <B_z>=-91+-35G. The calculated false alarm
probability values, 0.008 and 0.003, respectively, are above the value 10^{-3},
indicating no detection.
