Need help with quality of sprite particles in Niagara

Hello can some one tell me if is possible to increase the quality of this sprite particles?
They should be oval with transparent bg, but they look square.


This is the material:

This is the Niagara system with the emiter of the paticles:


If you’re using additive shading, you’ll need to multiply your particle color by the alpha/mask shape.

It works, ty!