Yes, this actually is possible!
Tested and running under Win8.1, latest drivers and a Hisense 55K680UAD UHD TV.
The trick is to keep the pixel clock to less than the 225Mhz HDMI maximum for this hardware.
Using CustomModeApp.exe (part of the Intel driver software) select the display and then go to advanced.
Use the following settings:
| Setting | Horizontal | Vertical |
|---|---|---|
| Front Porch | 48 | 3 |
| Back Porch | 80 | 23 |
| Sync Width | 32 | 5 |
| Active | 3840 | 2160 |
| Scan Rate | 25 |
Save.
This creates a dot clock of 221Mhz and relies on the display supporting 24Hz which is a scan rate used by blue-ray film.
Then using the Intel Display Panel (it will need to be re-opened to get the new setting), Select the new mode.
A reboot may be required for this resolution to be visible in the Windows Screen Resolution panel.