Sorry, no this is not possible.
Also you are using this Intent protocol wrong. As per http://developer.android.com/reference/android/content/Intent.html#ACTION_PICK this protocol expects that you put the content: URI of the data set you want the picker to select from.
That said, you should consider ACTION_PICK
deprecated. The modern action is ACTION_GET_CONTENT
which is much better supported; you will find support of ACTION_PICK
spotty and inconsistent. Unfortunately, ACTION_GET_CONTENT
also does not let you specify a directory.