How get classes that implements interface, but without inheriting interfaces

Let's say I have interfaces IA and IB:

public interface IA {}

public interface IB : IA {}

Now I want list of classes which implement directly IA, but without those implementing IB and others interfaces that are inherited from IA.

If I have classes Foo and Bar:

public class Foo : IA {}

public class Bar : IB {}

I want my code to return only Foo class. I think I can do it via reflection. I have method that returns list of all classes implementing IA, but now I don't know what to do next.

var types = Assembly.Load("abc").GetTypes();
return types.Where(i => typeof(IA).IsAssignableFrom(i) && i.IsClass);