  We report the discovery of an excess of main sequence turn-off stars in the
direction of the constellations of Eridanus and Phoenix from the first year
data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity
is centered around l~285 deg and b~-60 deg and spans at least 30 deg in
longitude and 10 deg in latitude. The Poisson significance of the detection is
at least 9 sigma. The stellar population in the overdense region is similar in
brightness and color to that of the nearby globular cluster NGC 1261,
indicating that the heliocentric distance of EriPhe is about d~16 kpc. The
extent of EriPhe in projection is therefore at least ~4 kpc by ~3 kpc. On the
sky, this overdensity is located between NGC 1261 and a new stellar stream
discovered by DES at a similar heliocentric distance, the so-called Phoenix
Stream. Given their similar distance and proximity to each other, it is
possible that these three structures may be kinematically associated.
Alternatively, the EriPhe overdensity is morphologically similar to the Virgo
overdensity and the Hercules-Aquila cloud, which also lie at a similar
Galactocentric distance. These three overdensities lie along a polar plane
separated by ~120 deg and may share a common origin. Spectroscopic follow-up
observations of the stars in EriPhe are required to fully understand the nature
of this overdensity.
