  There is a robust signal for a 511 keV photon line from the galactic center
which may originate from dark matter particles with masses of a few MeV. To
avoid the bounds from delayed recombination and from the absence of the line
from dwarf galaxies, in 2017, we have proposed a model in which dark matter
first decays into a pair of intermediate pico-charged particles $C\bar{C}$ with
a lifetime much larger than the age of the universe. The galactic magnetic
field accumulates the relativistic $C\bar{C}$ that eventually annihilate,
producing the $e^-e^+$ pair that give rise to the 511 keV line. The
relativistic pico-charged $C$ particles can scatter on the electrons inside the
direct dark matter search detectors imparting a recoil energy of $E_r
\sim$~keV. We show that this model can account for the electron recoil excess
recently reported by the XENON1T experiment. Moreover, we show that the XENON1T
electron recoil data sets the most stringent bound on the lifetime of the dark
matter within this model.
