[DataFormat.Error] External table is not in the expected format.

Community,

I am having a problem importing files from a sharepoint folder (6 files that need to be brought together). I see these as .xls files in Sharepoint and therefore use:

     let
         Source = Folder.Files(.... /sharepoint location".......),

// no problem
    #"Removed Other Columns" = Table.SelectColumns(Source,{"Content"}),
    #"Added Custom" = Table.AddColumn(#"Removed Other Columns", "GetExcelData", each Excel.Workbook([Content])),

//no problem - I am able to see all the data in PowerQuery

Everything looks fine - ready to go.

However, when I hit "Close and Apply" - the system returns an error:

     [DataFormat.Error] External table is not in the expected format.

The original files generated from a SQL query - and then the results of the query are pasted into an Excel file.... The orginal response that is being pasted is a tab delimited file - which may be causing the problem at some level.   

Is there a different approach I should be using to open these files? Instead of Excel.Workbook([Content}) is there a something else that will be more appropriate for a tab delimited file?

Thanks in advance.