SQL - error when using UNION

Here's my query:

Select top 1 ProductName, UnitPrice from Products
order by UnitPrice desc

UNION

Select top 1 ProductName, UnitPrice from Products
Where UnitPrice > 0
order by UnitPrice asc

I wanted to display the most expensive and the cheapest products in one table. That's why I used UNION to join the two queries. Unfortunately I get an error

Incorrect syntax near the keyword 'UNION'

That's why I'm asking for your help - what's wrong with my query?