Increasing resistivity of a metal

I am currently working with a "Cerro" bismuth-lead alloy. I'm using it because of its relatively high resistivity and low melting temperature
(255 F). What I would like to do is increase its resistivity. I'd like for it to be quite resistive without being a true insulator...on the order of a semiconductor.
What can I alloy or add to the metal that will be soluble and increase its resistivity substantially?
Thanks for any replies.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.