>>3106755>best 50mmCZ Sonnar T* 50mm f1.4 CY mount. You can get one in mint condition for about $300, MM version (has green max aperture number) is better than AE.
If you want a 35mm to have 52mm on your a6k then get the CZ Flektogon 35mm/2.4 or CZ Distagon T* 35mm/2.8. Both are great but the Flektogon is cheaper and has 18cm minimum focus distance which is great for macro.