My father was from San Luis Potosi and did some research into the Sandate surname. There are a lot of Sandate's in that area (San Luis Potosi/Gunajuato, etc.) but we are not in touch with any distant family there. With the help of the Morman curch records, though my dad found a marriage certificate dated 1760 in Mexcio of a De Sandate. We have not however been able to trace the name to Europe. We believe it may be Basque but have not confirmed it.