Unified search just search in one field

Hi,

We are using unified-search in one of our projects and in one specifc case I would like to search in just one field.
At the moment we have the following code which seems to search in more than just the one field.

_client.UnifiedSearch().For(search.Search).InField(x => x.SearchAuthors)

How can I search in just one field using unified-search?

Thanks in advance.

Regards,

Robert Baarda