[TYPO3-mvc] Urlencode within an argument declaration

[Robert Schneider]

Short question: What is wrong here?

<f:link.action
   action="listCategoryProducts"
   arguments="{category: '{'office & business' ->
               f:format.urnencode()}'">
   Office $ Business
</f:link.action>

I get the error message:

The argument "arguments" was registered with type "array", but is of 
type "string" in view helper "Tx_Fluid_ViewHelpers_Link_ActionViewHelper"

How can I create an array if not this way?

Robert