As of today, there are three standard autofocus primes for the Sony E-mount APS-C system with an approximate 50mm field of view*: the Sony E 35mm f/1.8 OSS, Sigma 30mm f/1.4 DC DN Contemporary and Sigma 30mm f/2.8 DN Art.
The popularity of the a5000 and a6000/a6300/a6500 series coupled with the affordability and suitability of these three primes for a variety of genres means that they are amongst the most sought-after lenses for any camera system.