We report the discovery of a candidate X-ray supernova remnant
SRGe~J003602.3+605421=G121.1-1.9 in the course of \textit{SRG}/eROSITA all-sky
survey. The object is located at (l,b)=(121.1 ,-1.9 ), is
arcmin in angular size and features nearly circular shape. Clear
variations in spectral shape of the X-ray emission across the object are
detected, with the emission from the inner (within 9') and outer (9'-18') parts
dominated by iron and oxygen/neon lines, respectively. The non-equilibrium
plasma emission model is capable of describing the spectrum of the outer part
with the initial gas temperature 0.1 keV, final temperature 0.5 keV and the
ionization age cm s. The observed spectrum of the
inner region is more complicated (plausibly due to the contribution of the
outer shell) and requires substantial overabundance of iron for all models we
have tried. The derived X-ray absorption equals to
cm , locating the object at the distance beyond 1.5 kpc, and implying its
the age yrs. No bright radio, infrared, H or
gamma-ray counterpart of this object have been found in the publicly-available
archival data. A model invoking a canonical erg SN Ia explosion in
the hot and tenuous medium in outer region of the Galaxy 9 kpc away might
explain the bulk of the observed features.This object might be a rare example
of an old SN Ia remnant in our Galaxy still bearing signatures of the ejecta
enrichment and probing the thermal and non-thermal properties of the hot phase
of the ISM above the cold disc. This scenario can be tested with future deep
X-ray and radio observations.