get all users from a group in Active Directory

I'm trying to get all users of a particular group in AD, then return a list of Employees as mapped to properties in my Employee class. I have:

My Filter is producing no results - what should it be?

Also, I tried the first solution here: List of users in specific Active Directory Distribution Group, but I need details such as mobile, extension, etc. which I couldn't get with that method.

public static List<Employee> CreateEmployeeList(string department)
{
    List<Employee> employees = new List<Employee>();
    string filter = string.Format("(&(ObjectClass=person)(memberOf=CN={0},OU=Users & Groups,OU=Blah,DC=Blah,DC=Blah,DC=Blah))", department);

    DirectoryEntry adRoot = new DirectoryEntry("LDAP://" + domain, null, null, AuthenticationTypes.Secure);
    DirectorySearcher searcher = new DirectorySearcher(adRoot);
    searcher.SearchScope = SearchScope.Subtree;
    searcher.ReferralChasing = ReferralChasingOption.All;
    searcher.Filter = filter;
    SearchResultCollection results = searcher.FindAll();

    foreach (SearchResult user in results)
    {
        // do whatever you need to do with the entry

        if (user != null)
        {
            UserDirectoryEntry = user.GetDirectoryEntry();
            string displayName = GetUserProperty("displayName");
            string firstName = GetUserProperty("givenName");
            string lastName = GetUserProperty("sn");
            string email = GetUserProperty("mail");
            string tel = GetUserProperty("telephonenumber");
            string extension = GetUserProperty("ipphone");
            string mobile = GetUserProperty("mobile");
            string title = GetUserProperty("description");
            employees.Add(new Employee{ FullName = displayName, FirstName = firstName, Surname = lastName, Email = email.ToLower(),