On the base of temperature dependencies of the specific heat in magnet
ic fields, thermal expansion and magnetic properties of high quality h
igh-T-c Ba1-xKXBiO3 (x=0,38 . 0,40) it was found that H-c2(T) had anom
alous upward curvature up to fields 20T and coefficient of thermal exp
ansion was negative at low temperatures. The results contradict the pi
cture of simple electron-phonon coupling. We have presented a model of
the electronic ordering in Ba1-xKXBiO3 which drives the system to the
dielectric-metal phase transition with doping. It was shown that elec
tronic spectrum peculiarities near the Brillouin zone boundary determi
ne the anomalous properties and upward curvature of H-c2(T) in BaKBiO.
The mechanism of BaKBiO superconductivity is discussed.