Yen stands out as haven in US debt drama:    - The yen has emerged as the preferred haven for investors worried by the stand-off in US debt talks
 - no sense of panic in foreign exchange markets, with investors assuming that US politicians will eventually strike a deal,
 - there has not yet been a general flight from currencies viewed as riskier
 - analysts expect a greater flight to haven currencies if talks drag on and say there is greatest immediate scope for flows into the yen