This version creates just the material prim and UsdPreviewSurface Shader.

import omni.kit.commands

omni.kit.commands.execute("CreatePreviewSurfaceMaterialPrim",
    mtl_path="/World/Looks/PreviewSurface",
    select_new_prim=True)

This version also creates UsdUVTexture Shader prims for the diffuse, roughness, metallic, and normal properties and connects them to the UsdPreviewSurface.

import omni.kit.commands

omni.kit.commands.execute("CreatePreviewSurfaceTextureMaterialPrim",
    mtl_path="/World/Looks/PreviewSurfaceWithTextures",
    select_new_prim=True)