Structure analysis is performed at 8K and room temperature in the isostruct
ural salts beta'-(Me(4)Z) [Pd(dmit)(2)](2) and beta'-(Et(2)Me(2)Z)[Pd(dmit)
(2)](2) (Z=P,Sb). The temperature effect on the dimerization of the Pd(dmit
)(2) molecules is measured. The electronic band calculations show that the
two-dimensional HOMO band remains the conduction band at low temperature as
the energy gap between the HOMO band and the LUMO band is increased.