Cannot cast list of internal class from another assembly in C#

I'm using a function from an external assembly that returns an object which is a list of an internal class and I cannot find a way to cast it in my code.

Code in the external assembly:

namespace AssemblyNamespace
{
    internal class InternalClass
    {
        protected internal byte b;
        protected internal int i;
    }

    public class PublicClass
    {
        public object PublicMethod()
        {
             return new List<InternalClass>();
        }
    }
}

My code:

using AssemblyNamespace;

static void Main()
{
    PublicClass P = new PublicClass();
    object obj = new object();

    obj = P.PublicMethod();

    // Is it possible to cast obj?
}

Is it possible to cast obj through reflection or something else? I took a look at question C# - How to access internal class from external assembly but could not find a way to use their suggestions.