  We checked consistency between the copper abundance derived in six metal-poor
stars using UV Cu II lines (which are assumed to form in LTE) and UV Cu I lines
(treated in NLTE). Our program stars cover the atmosphere parameters which are
typical for intermediate temperature dwarfs (effective temperature is in the
range from approximately 5800 to 6100 K, surface garvity is from 3.6 to 4.5,
metallicity is from about -1 to -2.6 dex). We obtained a good agreement between
abundance from these two sets of the lines, and this testifies about
reliability of our NLTE copper atomic model. We confirmed that no underabundace
of this element is seen at low metallicities (the mean [Cu/Fe] value is about
-0.2 dex, while as it follows from the previous LTE studies copper behaves as a
secondary element and [Cu/Fe] ratio in the range of [Fe/H from -2 to -3 dex
should be about -1 dex). According to our NLTE data the copper behaves as a
primary element at low metallicity regime. We also conclude that our new NLTE
copper abundance in metal-poor stars requires significant reconsideration of
this element yields in the explosive nucleosynthesis.
