  The antimatter components measured in the Cosmic Ray (CR) flux are thought as
secondary particles induced by the propagation of galactic CRs within the
galaxy. Recent results from the PAMELA experiment show an unexpected increase
of the positron electron ratio above 10 GeV. There could be different
interpretations to explain that result, the most discussed ones being the
signature of nearby compact astrophysical source(s) or of dark matter
annihilation/decay. Probing the positron-fraction rise above 100 GeV would help
to disentangle among different scenarios. Imaging Atmospheric Cherenkov
Telescopes (IACT) can extract the cosmic lepton signal from the hadronic CR
background between a few hundred GeV and a few TeV and reconstruct energy and
incident direction with a very good resolution. In addition, by using the
natural spectrometer formed by the Moon and the geomagnetic field, it is
possible to measure the positron/electron ratio at the TeV regime through the
observation of the CR Moon shadow. Despite the technique is particularly
challenging because of the high background light induced by the Moon and the
treatment of data, the MAGIC collaboration has performed for the first time
such observations in 2010 and 2011. Here we present the observation strategy
and the performance achieved during this campaign.
