I am using lightning design classes for visualforce pages. Each and everything is working perfectly only the issue is that i can't see the search icon for lookup field. Code:PO Box Address
Lookup filters in lightning are not same as the lookup filters in clasic. In lightnign It is like a search box.
To create search box you can follow the following link-
I can't see your code, but based on my experience, I had to add "/apexpages/slds/latest/" to the icon url path:
<use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/apexpages/slds/latest/assets/icons/utility-sprite/svg/symbols.svg#switch" />