Bad quality of Texture2d in inspector

Hello.

I'm trying to create custom inspector with high quality preview for Texture2d . Is there any way to improve it's quality? PS my Textures are 512x512 so there is no unnecessary scaling.

Code (CSharp):

1.         [HideLabel]
2.         [AssetList(Path = "/Content/SceenSetupGuide/")]
3.         [PreviewField(512, ObjectFieldAlignment.Center)]
4.         public Texture2D SingleObject;