TraceQL - Find all traces calling Serivce A but not Service B

Grafana Tempo
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Hi Grafana Community!

I wanna prove that 2 services are always called in combination and thought I could use TraceQL for that.

Selecting Traces that includes both services can be achieved with combining the span sets e.g.
{resource.service.name="A"} && {resource.service.name="B"}

Is there a way of retrieving all traces that only calls A or B?
Note, {resource.service.name="A"} && {resource.service.name!="B"} is not getting me the desired results as there are other spans in the trace fulfilling the filter.

Thank you in advance!