  For the first time, magnetoresistive properties of the single crystal of HgSe
with a low electron concentration were studied in wide range of temperature and
magnetic field. Some fundamental parameters of spectrum and scattering of
electrons were experimentally determined. Two important features of magnetic
transport were found - strong transverse magnetoresistance (MR) and negative
longitudinal MR, which can indicate the existence of the topological phase of
the Weyl semimetal (WSM) in HgSe. Taking this hypothesis into account we
suggest a modified band diagram of the mercury selenide at low electron
energies. The obtained results are essential for the deeper understanding of
both physics of gapless semiconductors and WSMs - promising materials for
various applications in electronics, spintronics, computer and laser
technologies.
