How to access discovery.svc service, if it needs authorisation (MS Forefront)?

I have an URL like https://crm.xxxx.com/XRMServices/2011/Discovery.svc and I want to discover an organisation with my client. But if I open this URL in a browser window, I will get an authorisation screen:

I get an exception, If I try to add this url on client to following method as parameter "url":  

ServiceConfigurationFactory.CreateManagement<T>(new Uri(url));

Exception:  Metadata contains a reference that cannot be resolved: "https://crm.xxxx.com/XRMServices/2011/Discovery.svc?wsdl".

or

Exception:  Metadata contains a reference that cannot be resolved: "https://crm.xxxx.com/XRMServices/2011/Organisation.svc?wsdl".


How to pass through this authentication?