  In this paper we report an exhaustive experimental work on magnetoresistance
effects found in a system in which a large number of nanocontacts are produced
between oxidized Fe fine particles. We have obtained the following
performances: i) Huge low field room temperature magnetoresistance (over
1000%). ii) Non-linear I-V at different applied fields and temperatures. iii)
Large thermal stability and reproducible resistance value under thermal cycles
from room temperature down to 5 K. iv) Easy to fabricate with an almost 100%
success. v) Heavy duty and transportable samples with reproducibility tested in
several laboratories. We realized that the extraordinary effect found is
related to the oxygen content at the particles surface
