Invalid route action [Auth\\SignInController] "UnexpectedValueExpection"

I am having a problem with routes. I have created SignIncontroller with the __invoke action and registered its routes on route/api.

My api.php code

<?php

use Illuminate\Support\Facades\Route;


Route::group(['prefix' => 'auth', 'namespace' => 'Auth'], function () {
    Route::post('signin', 'SignInController');
    Route::post('signout', 'SignOutController');

    Route::get('me', 'MeController');
});

I have also created the three routes with __invoke for testing

My SignIncontroller code

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use Illuminate\Http\Request;

class SignInController extends Controller
{
    public function __invoke()
    {
        dd('Sign In');
    }
}

If I run on postman I get below error

The error