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LONDON, April 24 (Reuters) - European shares had a choppy opening on Tuesday as a batch of first-quarter corporate results failed to set a clear trend, and chipmakers were weighed down by AMS' warning of a downturn in orders. The pan-European STOXX 600 was up 0.16 percent by 0735 GMT after spending some time in negative territory as it moved towards a heavy week of earnings.
Austria-based chipmaker and Apple supplier AMS tumbled about 10 percent after reporting lower orders from one of its main customers which it did not name, sending shares in other companies in the sector down.
"It is reasonable to assume that this will have a negative impact on STM's Q2 guidance as well", Liberum analysts said as shares in STMicro fell 2.3 percent and peer Dialog Semi tumbled 4.1 percent.
These results come as a strong growth in ad sales for Google despite a surge in costs at its parent Alphabet brought some relief to the sector after a ropey few months for the leading U.S. tech companies.
Germany's SAP rose 3.5 percent after saying it was gaining ground on competitors Salesforce and Oracle in the cloud and that its margin recovery was firmly on track. (Reporting by Julien Ponthus Editing by Andrew Heavens)