It is allowed. (Unless I misunderstood your statement).
From Google AdSense FAQ:
8. Can I display AdSense for search and Google ads on the same web page?
Yes. You can place an AdSense for search box on any page that meets our program policies, even if you're already showing Google ads on that page. Searches from the AdSense for search box will lead to a Google-hosted results page that is also monetized with Google ads, allowing you to monetize all aspects of your site.