How to include 'reference'-field from the combinations to the search-index

[Xedd]

Hello,

I can't get this to work.
I want to include the reference-field of the combinations to the search-index.
[ ps_product_attribute > reference ]
If people know the reference-code, they should find the object where the reference is part of.
(and if possible with the choices made for them.)

Can someone help me with this, or at least point me in the right direction?

Kind regards,

Xedd