  Organic molecules have recently revolutionized ways to create new spintronic
devices. Despite intense studies, the statistics of tunneling electrons through
organic barriers remains unclear. Here we investigate conductance and shot
noise in magnetic tunnel junctions with PTCDA barriers a few nm thick. For
junctions in the electron tunneling regime, with magnetoresistance ratios
between 10 and 40\%, we observe superpoissonian shot noise. The Fano factor
exceeds in 1.5-2 times the maximum values reported for magnetic tunnel
junctions with inorganic barriers, indicating spin dependent bunching in
tunneling. We explain our main findings in terms of a model which includes
tunneling through a two level (or multilevel) system, originated from
interfacial bonds of the PTCDA molecules. Our results suggest that interfaces
play an important role in the control of shot noise when electrons tunnel
through organic barriers.
