How do I design an employee manager relationship class diagram

Assume everybody in the company is an Employee:

public interface IEmployeeInfo
{
    string Name {set; get;}
    string Address {set; get;}
    decimal Salary { set; get; }
}

public interface IEmployee : IEmployeeInfo
{
    string Title{set; get;}
    IManager EManager { set; get; }
}
    
public interface IManager : IEmployee
{
    List<IEmployee> EmployeesManaged {set; }

    void AddManagedEmployee(IEmployee employee);
    void RemoveManagedEmployee(IEmployee employee);
    bool IsManagedBy(IEmployee employee);
}

Then 'Employee would inherit from IEmployee, and 'Manager would inherit from IManager.

Note the 'set only property 'EmployeesManaged in 'IManager: assuming you want to encapsulate the usage of that List, you can use an explicit interface implementation in the Manager class:

private List<IEmployee> EmployeesManaged { get; set; }

// implicit interface impl.
List<IEmployee> IManager.EmployeesManaged
{
    set => this.EmployeesManaged = value;
}

Then, only internal methods of 'Manager can access the List:

public void AddManagedEmployee(IEmployee employee)
{
    if (IsManagedBy(employee))
    {
        // throw error ?
    }
    else
    {
        EmployeesManaged.Add(employee);
        employee.EManager = this;
    }
}