Scaling with 4k Display

[Cykoh]

Dear all

I've a Dell USB 3.0 D3100 docking station and a 4k Samsung U28E590D Display.
The dock is connected to a Macbook pro Retina early 2012. Everything is working, the only thing what doesn't work is the scaling in OS X for the 4k Display.

Is there a workaround to activate this scaling?

I've attached a print screen with the menu for the internal and external display.

Thank you very much.

regards
Cyrill