On this map describing the railway lines in Eastern Japan where Suica and other compatible IC cards can be used, it is noted that a star indicates that
In addition to the above, Suica's service is partially available in some other stations. For further details, please access the JR EAST website.
For example, the Ban'etsu West line, running westwards from Koriyama station (at the bottom right corner of the PDF), is marked with a star. I assume that this means that Suica can only be used at some stations on this line, but where exactly on the JR East website do I find out exactly what those stations are?