  We used high resolution angle-resolved photoemission spectroscopy to reveal
the Fermi surface and key transport parameters of the metallic state of the
layered Colossal Magnetoresistive (CMR) oxide La1.2Sr1.8Mn2O7. With these
parameters the calculated in-plane conductivity is nearly one order of
magnitude larger than the measured DC conductivity. This discrepancy can be
accounted for by including the pseudogap which removes at least 90% of the
spectral weight at the Fermi energy. Key to the pseudogap and many other
properties are the parallel straight Fermi surface sections which are highly
susceptible to nesting instabilities. These nesting instabilities produce
nanoscale fluctuating charge/orbital modulations which cooperate with
Jahn-Teller distortions and compete with the electron itinerancy favored by
double exchange.
