Dax- How to make a If Statement with multiple results for one condtions

i trying to programm some row level secruity in SSAS with Dax funtions.

my idea is that one employee can see the data from more than he can see. I this case Bob can see his data, but also the data his Collegue Lars can see. We created a Fact-view-table where we attached a domainname so its easier for us to filter in the RLS

=Sales[DomainName]= IF(USERNAME()="Bob",{"Bob","Lars"},USERNAME())

But if i wanna test via PowerBi hes says

A table of multiple values was supplied where a single value was expected

what did i forget?