Is it good reputation for a researcher to publish an article belonging to different research field?
Since the fields are so far apart, a publication in one might not help you in the other, specifically. However getting some research experience is both worth the effort and will be looked on positively. In addition to being relevant to some field, research involves a process requiring focus and discipline. 

I'd only recommend against this if the time involved would take you away from your mainline trajectory. 

The publication won't hurt you. The experience will help. But it takes time and effort.