I was looking for it last night but could not find the solution. I want to have down to 1-minute charts, do I do the following with IntervalType="Minutes"?
<chart:SfChart.PrimaryAxis>
<chart:DateTimeCategoryAxis Interval="1" IntervalType="Minutes" Header="Primary"
EnableScrollBar="True" LabelFormat="hh:mm:ss" />
</chart:SfChart.PrimaryAxis>